The title is a common statement usually thrown at people who are complaining about stuff in their life. Now, I don't completely agree with this statement. Why don't I fully agree with it? Because things happen in life which are beyond anyone's control. For example your car breaking down. Unavoidable even if you are a person who does look after your car, it can still fail. Illness, We never want to be sick but again it's one of things in life that happens to everyone, even if you're a clean freak you are not immune to falling ill. many things in life happen which are beyond our control.
So, I think the statement is only half true.
Also, there are things in life we may like to do, such as a dream job but half to make do with what we can get, is that our own fault? Maybe, maybe not depending on i9ndividual people. There are things I'd like to do but can't due to health. I'd like to be a firefighter but I wouldn't be much use with a dodgy knee, the last thing I'd want is to be carrying someone down a ladder and have my knee give out from under me.
I prefer the saying "Shit happens" more than "Life is what you make it" because "shit happens" is a far more accurate saying.