How do I redeem myself from all the horrible things I’ve done in my life?

For the longest time I’ve been selfish with those I care about in my life. All I’ve ever known in my life was self interest, manipulation, pessimism, anger, hate, lack of sympathy and empathy for others, not caring about others opinions, being too blunt, and other things. I don’t really have a good relationship with anyone in my life, but they’re still there for whatever reason. I’m emotionally, and mentally immature. When it comes to sense of humor I can dish it out but can’t take it. I use negativity as humor. I put other people down. I can just go on and on and on about all of the horrible things I have done and do to others who don’t deserve it. Please don’t try to make me feel better because I know I’m a horrendous human being, if you can even call me human. How can I redeem myself from the evils of the past and create a brighter future for myself and others around me?