How to get over people and love yourself.

I keep thinking of people that did me wrong, I keep thinking of rekindling friendships with people who don't even care about me, but I feel like I care too much, maybe because I am insecure or scared to be alone, but it feels like I haven't ever gotten over anyone that has been the smallest part of my life, why am I so easily moved, it's making me depressed. I think about people I haven't seen in years, who don't care for me, but I'm the one getting depressed over them, reaching out to follow them on instagram when they rlly couldn't give less of a shit, in the end I get my feelings hurt over and over. Please any advice would be good, this is exactly how my ex had so much influence over me, because I cared way too much, I think it all stems from my own insecurity. i really need advice on how to glow up past this attitude and become an idgaf baddie plsssssss