How do you stop overthinking your life?

I'm 22, recently finished 3 years of mandatory army service, got a job a month after (been 6 months since). Got depression, got out of it, for the most part at least (therapy, medication and mom losing days of sleep on the count of having to hear me out). I LOVE stories about people just being happy, it gives me hope that one day I will also achieve it. My question is: is the reason people are generally not sad that they take life as is? I know I don't like where I'm at right now, I just don't see it changing in the immediate future.