how come life isnt working out

36/M

After all these years I look back and feel like life has been nothing but a hurtful disappointment. I've been betrayed by friends, cheated on by partners, failed at different careers, feel like I have no purpose. I have every reason to be happy, but for some reason the rain cloud keeps dumping on me. People take advantage of me, seems like no one respects me, and I cant get ahead. Why is it that no one takes me seriously, I'm not sure I even take myself seriously at this point. How can I turn this around.