They are hurt and I did it

I had the best most wonderful relationship with the most amazing caring person . It was a 3 year relationship and I took liberties we were lving together and about to get married . I have a lot of problems and I mean a lot so I go into self destructive mode and end up hurting those around me that I love because I was hurting so much inside so instead of waking up happy I was always moody which obviously took it out on my ex because its exhausting living with someone who's moody all the time . It got to a point where she said she's sad all the time because I'm sad so we broke things off and I know she's better off for it because I was dragging her down with me because of my own problems . And I know no matter what I do now I can never win her back and now I'm worried if I've lost the person I love with all my heart how can I find a new person because no one could ever replace her