I'm by no means an expert, but I've felt pretty empty and worthless before, for about a year. Wouldn't wish depression on many people. I've since improved to the point where I don't think I'll ever return to a point as low as I did then.
I think the biggest difference for me was actually split into two things. Having people you can love and who love you is very important but the most important factor in your well being is you.
Love/Passion - The things that you think about. For me it can be my endless love for the complexity of music/sports/my religion or anything that I spend my time with. It's almost like a drive that pushes beyond despair. They bring me away from myself and my confusing, but unrelenting pain and into something else. Something that I love. Despite the importance in finding something worth your time, these are still just things.
Peace - At some point in life, most people realize that they won't become some influential person, forever remembered with a legacy, that will last 1000's of years. For most people, that's by their early twenties or late teen. It's important to be okay with the fact that while everybody is special and talented in their own way, you might not be the most recognized person in the world. I think through that gloomy thought, I was able to try to make the best out of the ordinary things I experience daily. It changes my perspective of myself. I feel like I can just live to my best without some outer pressure.
Find something or someone, just one thing you love, and surround yourself with it. Keep to a routine. If it doesn't work, do something random. Surprise yourself by trying something you've never done before. Push to spend time with someone, and it can be anyone. Don't look at your realistic lense of the world as being a negative thing, but don't just think of it as being better than anyone else's. The world has gaping flaws and problems but look beyond that, and out to the sky and stars.
Honestly I have no idea where I'm going with anything I've said, but one of the things that different with me now is learning to take things a little less seriously. That's the biggest difference I've noticed within myself.