Evidence Over Enthusiasm

There’s a particular kind of person who tells you they’ve “got a really good feeling” about something. A new diet, a new investment, a new opportunity a friend mentioned last week. I used to be that person more often than I’d like to admit, and after four decades in business I’ve learned to be suspicious of my own good feelings, especially the strong ones.

Enthusiasm is cheap. It costs nothing to feel excited about something, you can generate it on a walk, in a conversation, at two in the morning scrolling through an idea that suddenly seems obvious. Evidence costs something. It takes time to gather, patience to interpret, and occasionally the discomfort of finding out you were wrong before you’d spent too much finding out the hard way. That trade is worth making every time, and it seems to me most people never learn to make it, not because they’re careless, but because nobody ever sat them down and taught them the difference between a feeling and a fact.

The organisational psychologist Adam Grant uses a great example of how the presentation of “facts” carries trust. A teacher handed her students an extract from a 1940’s history textbook, and some students accepted the content without question, because it came from a textbook, and textbooks are where facts live. Others noticed the errors and the gaps straightaway and started asking whose version of events they’d actually been given, and whose had been left out. Grant’s point is a simple one: once we’ve heard a story from a source we trust and accepted it as true, we rarely go back and check it again. That’s not a flaw specific to schoolchildren with an old textbook. We trust the truth of advice from a colleague we respect, an opinion repeated often enough, or a decision a friend has made and who expresses happiness in it. The story gets accepted as a fact the moment someone we trust tells it to us, and it stays that way indefinitely simply because nobody circled back to check.

I watched this play out for years in business before I understood what I was watching. Someone joins a gym in January full of conviction, and by March the conviction has evaporated because nothing was ever measured, so there was nothing to notice improving. Someone else starts a side business on a hunch about what the market wants, spends eighteen months building it, and only then asks anyone who might actually buy it whether they would. The pattern repeats everywhere. Enthusiasm gets you started. It almost never gets you finished, because it has nothing to hold onto once the initial feeling fades, and feelings always fade.

Measure. Improve. Validate.

I run my own health this way now, not by hoping something is working, but by testing, adjusting, and testing again. Blood markers, not vibes. Years ago I had an Omega-3 test done that came back lower than I expected, changed what I was taking, and retested. The number moved. That’s a small thing on its own, one data point, but it did something bigger than fix a ratio on a lab report. It changed how I approach everything else, because once you’ve seen a number move in response to something you did on purpose, you stop trusting your gut, or somebody else’s, quite so easily. You start asking, of nearly every decision, “how would I actually know if this is working?”

That question is the whole discipline. The essence of it is in its objectivity — the one that comes from measurement, not “how do I feel about this?” which is how enthusiasm rules reality. The friend who recommended something or offered an opinion is looking at it through their lens, and it’s received wisdom. Being objective simply begs the question “how would I know,” which is harder to answer and far more useful, because it forces you to define what success would actually look like, rather than borrowing someone else’s conclusion and calling it your own.

The pattern has a shape to it, and it’s the same shape whether you’re managing your health, your money, or a decision about how you spend your Tuesday evenings from now on.

Measure. Improve. Validate.

One of the first things I was taught in my first “real” job was “if you can’t measure it, you can’t manage it.” Where you actually are, not where you assume you are because the adopted opinion, and the consequent assumption, is where most bad decisions begin. One change at a time makes the consequence of the change measurable, and then reassess to validate improvement. A deliberate stage process of change and improvement leverages results or points the way to something else. Doing everything at once tells you nothing about which one mattered. Most people skip the steps. It’s just what happens when life is busy and a decision feels good enough to run with, and checking doesn’t seem to be important when there’s always something more urgent than the time it would take to check. But “feels good enough” is exactly the standard that leaves people three years into something that was never going to work, wondering why the enthusiasm ran out before the evidence ever arrived to replace it.

There’s a version of this that shows up in how people size up an opportunity, too, business or otherwise. Someone hears about something that sounds interesting, watches a few videos, talks to one person who’s excited about it, and either dives in or walks away, all inside a week, all without ever laying eyes on an actual number. Compare that to how the same person would buy a car. They’d check the mileage and the service history, maybe get it independently inspected, because a car purchase is a big decision and the impact of a poor choice can be significant in time and money. The recommendation of a friend carries real weight for most of us and it is a valuable start point, but it also seems to be the point at which so many of us stop being objective, to the extent that regrettable decisions get made on enthusiasm alone, rather than “is it right for me?”

The Signal

A pattern worth naming plainly this week: people are getting much better at measuring themselves, and no better at acting on what they measure.

79% of UK adults now track at least one aspect of their own health or wellbeing, according to recent NHS-linked research, up sharply from a decade ago when this kind of self-monitoring barely existed outside a GP’s surgery. Blood pressure is the most commonly tracked measure, followed by fitness and exercise, and most people say they trust the results once they have them. The tools have never been more accessible or more accurate.

A separate study of 2,000 UK adults found that a quarter of people who track their health have no real idea what the numbers mean, and nearly a quarter admit they’ve ignored a health alert from their own device altogether — heart rate, activity, and stress warnings being the ones most commonly waved away. Measuring isn’t the hard part any more. Interpreting the measurement, and actually acting on it, still is.

On the business side, 35 to 42% of UK business failures are traced back to a simple, avoidable cause: nobody validated whether there was real demand before committing to the overhead of trying to serve it. The ONS’s own figures put the five-year survival rate for a UK business at 38.4%, which means more than six in ten businesses started in a given year won’t see their fifth birthday. Most of those businesses weren’t undone by a bad idea. They were undone by an idea nobody tested before betting the mortgage on it — enthusiasm, or a friend’s confident opinion, carried a long way past the point where a simple question, asked early, could have saved a great deal of time and money.

There is a marked rise in the number of UK adults adopting a side hustle, not surprisingly perhaps given economic circumstances. 39% had some form of side business in 2025; it is now 46% according to a Finder UK study. This is important to understand in the context of this piece; a side hustle is the first foray for a lot of people into the world of a business of their own, and its success is dependent on organised, planned activity.

Those that succeed do so by keeping score and compounding results over time, not by diving in with time-dated enthusiasm.

Resilience, in health or in money, isn’t built by feeling certain about something, or by trusting that somebody else already checked. It’s built by testing certainty through measuring, adjusting, and measuring again — steadily, long before anyone’s watching and long after the initial excitement has worn off. That’s a less exciting story than the one enthusiasm tells about itself, but it’s the one that’s still standing five years later, which is the only review that actually matters.

This Week’s DMO

Pick one thing in your life you’re currently running on enthusiasm, or somebody else’s say-so, rather than evidence — a habit, a decision, a piece of received wisdom you’ve been carrying quietly without ever checking. Find one number that would actually tell you whether it’s true. Write it down this week. Not to prove yourself right. To find out.