The Big 3

A wise friend of mine once told me: if you're not happy with how your life is going, think about changing one of these things: who you're with, where you live, or what you do for work.

I'm no expert on living happily but I think this was good advice. And also that I think it can be non-obvious which of these are making you unhappy: e.g. you think you hate your job, but really you just hate your city, and if you moved elsewhere you'd find the same job pleasant.