When feeling worthless
Everyone is born differently and we should embrace our uniqueness.
Comparing yourself to others is common and downgrading ourselves doesn't make life any easier. It doesn't make anything better. We need to fall in love with ourselves and just remain content with who we are. Worrying about other people is completely pointless in the long run.
Don't listen to others negativity.
It only beats you up inside.
Be content with the past and present. Only 'you' can make it better.
You can't hate yourself into loving yourself. How is that even possible?
It may take time but, you should learn to appreciate how you are as a human being. Or develop into a person you wish to be.
It's no good feeling sorry for yourself.
Depression/SADNESS can make you want to hide away from the world and disappear. It’s okay to take some time out but give yourself a time limit and then do something productive to improve your mood. Depression can be well managed (I know this from personal experience) and there can be a wonderful life beyond feeling worthless.
Feeling lonely is the worst. That feeling comes to me nearly everyday. You can't help people leaving your life. You can be a kind person. A kind of person that gives them a reason to stay. However, I don't want to feel and nor does anyone else, that friends only want you there because you do things for them. As if you're a slave.
That's not real friendship. A real friend wants you around because they think you make their life happier. Not just easier. Same with a boyfriend/girlfriend.
I'll end with this:
Every life is priceless. Spend your life being/doing what you love.