After working very hard on things to 'make money' (no goal attached, just making money, boy I was naive) doing stuff I really didn't like to do (building large EJB based systems for banks/insurance and we had entity beans back then!), I had some realisation that actually, this sucks. I alienated my gf at the time, my friends, my family. I worked, 200+ people under me and it sucked. I thought about it a few days, sold off some stock to make sure I could have freedom.
Which I also believe is the main goal of having money. No loans/mortgages, being able to do what you want. And then I started making companies again, doing about the same thing (without the entity beans, or beans at all :), but now it's fun. If it goes badly (the current crisis almost bankrupted one of my companies) I handle it like you are supposed to handle it; in a calculated, company-first, manner. And pull through stronger than before. If you don't have that freedom, you make decisions which often don't reflect the best interest of the company because, well, you cannot pay the rent or feed your family.
I always believed in lots of interests and hobbies (my twitter feed must seem rather ADD, but I actually have a planned working day in which I get to do those things) as I think the biggest waste of life you can have is boredom and now I actually get to make companies around those things. Money in the bank gives you the balls and the contacts to do that while as before that wasn't even an option without right-out prostituting yourself. And the freedom to say no to something which would before have been (or have seemed like) a brilliant opportunity because you just don't want to.
Freedom usually (unless there are health issues in your family/close friends) also buys you no stress which already comes from the above. But having my own fruit/vegetable garden and having the time to prune the trees and prepare nice food from it etc is very far removed from shit in styrofoam containers and not even tasting it during a client conference call.
Edit: I forgot my new-found pet peeve with getting older; people get way to serious over 30. Life's a game and a short ride; money allows you to live it like that.