If you could only keep one mental model, keep compounding.
Not the financial kind — although that’s where most people learn the word. The general kind: small things that build on each other over time, where each unit of input produces more output than the last.
It applies everywhere. Skills compound: learning one thing makes the next thing easier, not linearly but exponentially — the person who understands statistics, programming, and business doesn’t have three skills, they have a superpower that none of those skills produce alone. Reputation compounds: every honest interaction builds trust and every kept promise makes the next one more believable, and it accrues so slowly that most people don’t notice until they need a favour and discover they’ve been building credit for years. Writing compounds: the first post is terrible, the tenth is okay, the fiftieth is good — not because you studied writing but because each post taught you something the previous one couldn’t, voice and frameworks and audience all compounding at once. And tools compound: every system you build makes the next one faster, the pipeline you built last month becomes the foundation for this month’s project, and the naming convention you chose becomes an identity.
If compounding is the model, the decision framework writes itself: does this compound? A job that builds transferable skills compounds; a job that pays well but teaches nothing doesn’t. An honest relationship compounds trust; a transactional one doesn’t. Deep thinking compounds into better judgment; organising your organisation doesn’t. Writing publicly compounds — audience, ideas, reputation, all at once — while writing in private notebooks doesn’t, or compounds much more slowly.
The trap is confusing activity with compounding. Not everything that feels productive actually builds on itself. Some work is linear: you do it, it’s done, nothing carries forward — meetings, most emails, administrative tasks, all consuming time without producing compound returns. The discipline is asking, regularly, of everything you’re doing: what actually compounds? Then doing more of that and less of everything else.
There’s an uncomfortable corollary. If compounding works for good things, it works for bad things too. Bad habits compound. Distrust compounds. Technical debt compounds. Small lies compound into a reputation you can’t escape. The model doesn’t care about your intentions; it just multiplies whatever you feed it. So choose carefully what you compound.