"Nobody really cares if you're miserable, so you might as well be happy."
Don't give up. There will always be a tommorrow. Another chance. Find that happy thing in your life. Stick with the things that make your happy. Don't always make yourself a martyr. You have to take time to make yourself happy first. Don't try to find love in places it doesn't exist. Try somewhere else if you really want it, or maybe take some time to love yourself. Don't fall into funks, because they tend to not want to let you go. Screw the past. It's gone, theres nothing you can do. Don't ignore old-friends if they are trying to make amends. Sometimes part of the blame is on ourselves. You are only who you perceive yourself to be. Try to see yourself as who you want to be. Set a goal. Maybe for the week, maybe for the day, set a short time attainable goal or goals and strive to reach them. Your concentrated efforts can do wonders. Find someone to listen. Find someone who won't criticize or start to talk about themselves. Someone who can give you some advice but not make you feel insignificant.