Should you marry that person? Quit a steady career to retrain? Move across the country, away from aging parents? Sit with any of these and watch your mind spin. You weigh what you'd gain against what you'd lose. You run the numbers. And still no answer arrives.

Big decisions do this to us. They are rare, life-shaping and hard to undo, and they refuse to be solved like a sum.

Researchers recently used AI to analyze more than 100,000 real dilemmas posted online. They found choices pulled in dozens of directions at once, far from the tidy two or three variables we imagine. Big decisions are messier than they look.

I study how people make life's biggest decisions. In research, I asked more than 600 people to describe their 10 biggest decisions. Thousands more have since mapped their own choices in an ongoing study. Marriage, children, career changes, house purchases and relocations come up again and again.

My study didn't hand me a checklist you can use when faced with a big decision. But it did show what separates the decisions people are later glad of from those they regretted. Read alongside the wider research, those factors fall into a rough order worth trying.