Advice? How do you get over it?

I just put my two weeks in for my 3rd job (I still have 2) I’m sad and think I’ll regret it...it’s what’s best for me though, been there a year and a 1/2. Management is bad, they play favorites, I dread going to work every morning but for some reason it still just doesn’t sit right with me...maybe because I’ve never quit a job before? I’m losing money?... I just don’t know how I feel about it but I know its what’s best for me :(