I get the feeling that I'm at the end of my rope and can't muster the strength to hold on.
I'm sorry to hear this. Why do you think you feel this way?
I've screwed up too badly.
It's important that we try and stay strong, even in the darkest of times. I hope you agree that you won't give up on yourself.
Life sucks and I hate it.
I think it would be a good idea for you to talk to a therapist or other mental health professional about what you're going through, because I think you might be suffering from depression. I think talking to someone could really make you feel better.