What seemed like a small or inconsequential decision at the time, but actually ended up having a big impact later on?

I was talking with my high school girlfriend about future career ideas and she mentioned one that made me think, "Huh, I never thought about that." So I decided to read about it at the school library during lunch one day.

I can directly tie my college degree, all the places I've lived, most of my friends, half the countries I've traveled to, and meeting my spouse all back to that one moment.