Because the grim truth is that for every one who does succeed, there are a thousand who have faith, work hard, give it a try and die broke.
The only thing you can manage for yourself every time is to be happy. The only thing you need to do that is the guts and good humour to either take your happiness in what you have or are right now. or if the situation is too toxic, get out of it.
Material or financial success is not the only measure of happiness. Indeed, wealth is not the only indicator of success. I've got three beautiful grandkids, so who cares if the bank balance is wobbly sometimes? I'll take a cuddle from them over cash anytime!