Not everything needs to be explained. Not everything needs to have a reason to happen. And most certainly nothing needs to be explained for you. The search for a rationale for anything that has happened is often as useless as worrying about the things that haven't happened yet.
Spend less of your time trying to figure out a culprit and move forward with your day. Don't worry about things you can't change, and instead make sure to notice the things in which you can affect a change.
Be a rational realist optimist.
Examine and dissect and question and study. Accept nothing except everything.
Look at the world as it is, not as you wish it to be. Revel in the strengths that you have, instead of pining for the rewards of the strengths of others. Enjoy the moment whenever you can, and this takes practice.
Whenever you are walking down the street with someone else, and you think about how beautiful a tree or a building or a woman or a puppy is, say it out loud. Include the world around you in your moment of joy. Don't be selfish with your pleasant outlook on life. Smile at someone.
Give when you can, and hoard until you don't need to. Be open to fun nights. Tell people "no" every once in a while, but don't dissemble about why. Take a night for yourself. Be honest with yourself more than anyone else. Stop calling them cheat days. Do what you want, and if you want to change DO IT.
If you want to change do it. It doesn't have to happen all at once. Set a date and stick to it. Start small and work your way up. Practice takes time and you have to practice this change. Baby steps. Do a little every day. Clean one corner of one room every day. Do 5 push-ups every morning.
Love yourself enough to be appropriately selfish, and then give the rest to others.