Expressing success is normally done in terms of money. It’s easy.
The money yardstick is the universal language for success, in the States at least. But it’s not descriptive or good at indicating how happy that successful person is. Someone who’s wildly successful could be happy or could be unhappy, same thing for someone without lots of money.
Maybe we need a word for “never having to ____,” or an expression capturing the level of success you have when you do exactly what you love every day.
If someone gets up when he likes and does what he loves and can avoid the things lots of numerically successful people complain about all the time, like commuting, being over scheduled, having harsh deadlines, dealing with committees, etc., what do you call it?
Having a good life. Maybe? That’s what’s important. And you can have a good life whether you’re rich or not.