Describe a difficult decision you once made.

The decision I'd like to talk about is leaving my first company — a big, stable firm — for a small startup, about five years ago.
On paper it made no sense. I had a secure position, a predictable career ladder, and parents who were proud of the company name. The startup offered a lower salary, longer hours, and a real chance of simply not existing in two years. But the work itself was exactly what I wanted to be doing, and at the big company I could see my next twenty years laid out with depressing clarity.
I agonised over it for about two months. I made spreadsheets weighing up the pros and cons, asked everyone I trusted — and got perfectly contradictory advice. In the end, what settled it was a single question a friend asked me: which choice would I regret at sixty? Framed that way, it wasn't close. I took the plunge.
The result was messy but right. The startup did struggle, and there were genuinely frightening months. But I learned more in two years there than in seven at the big firm, and every opportunity I've had since traces back to that jump. In hindsight, it was the turning point of my career.