So you think you got past it all, back when you were a kid, dealing with hormones, social ladders, getting good grades in school, watching your parents rip themselves to pieces (either together or separately). Well, guess what?
It doesn't end. It doesn't always get worse, but it definitely doesn't end.
This is not fatalism or bad news. It's just a fact of life. If the life you live is really like school (you learn something new each day), then everyone else's lives are your tests. Each test is handed to you with the foregone conclusion that you have the potential to pass it. Certainly, anyone can fail a test, but passing takes effort.
Back in school, when faced with a particularly difficult math test or pop quiz, what was your reaction upon finding out that you passed? That fucker was tough, but you did it, you passed. Perhaps you didn't whoop for joy or dance in the halls with elation, but you had to feel at least a little good about passing.
The surest way to fail a test is not to face it. To quote Wayne Gretzky, "You miss one hundred percent of the shots you don't take."
Every day and every experience we have can be and often is a test. If, at the close of your day, you don't feel like you've done anything worthwhile, like you've passed, then take a review and figure out how/why. Keep mindful of that and don't let it happen again. You'll be tested again and again until you get it right.
Continually saying that you're a failure is setting yourself up to fail.
As long as you say you aren't capable of doing anything, your unconscious mind is listening and it listens closely to what you say. It will regard what you say, even to others, as an order. Keep saying negative things about yourself and your unconscious mind will take that as an order to perform negatively.
"I'll never be happy."
"I'll never fall in love."
"I'll never be as good as X-person."
"I'll never feel content with myself."
Sound familiar? Do you really want to tell yourself these things? Would you want to hear them from someone you care about? When you talk, listen to the things you say, as though someone else is saying them. When you do something, reflect upon it as though it was done by someone else. Is what you say and do something you'd like to share with others? Would you rather spread the wealth or spread a disease?
Depression is not the new, hip drug. It's been around for centuries and its history is fraught with horrible outcomes.
You have a choice: you can either carry on with spreading negativity or you can effect something positive in this world. Your actions speak louder than words and the world is watching.