I'm getting to this point in my life right now. Realising and trying to accept happiness is a state of mind. It's rather new to me and it's a struggle most days. Any advice?
I try to remember that I live in the absolute best times in history. 200 years ago, even kings couldn't live as well as I do, now. I've got air conditioning. I've got running water that is both hot AND cold. None of my family died from tuberculosis. I can be reasonably sure nobody is going to invade my country and kill my kin. I don't personally know anyone who has ever had dysentery.
And sometimes I just wallow in sadness. It feels good sometimes. Sleep in. Eat a cheeseburger. Eat 3 cheeseburgers. Play a video game. Play a video game for 5 hours. Sometimes things have to get worse before they are big enough to get rid of.
It's a conscious decision, every day. That's part of why I go by "moron4hire". It's a reminder that, despite my ambitions and my progress, I'm a base idiot compared to some other people. I still work and try to do more, but it's because I know that it will help people, not because it will make me happy.