We're conditioned to ensure relationships end amicably in a way you can still be friends afterward. Sometimes, sure. If it was just a casual, healthy relationship that ended mutually, still being friends is okay. However, if it didn't end so peachy, don't be afraid to hit that block button. You need to stop checking up on people who hurt you.
If you're like me, you constantly seek out approval from everyone. You want to constantly be on good terms with every relationship in your life, with every person you know. It doesn't matter if it's some random old lady at the coffee shop you frequent or a former best friend who backstabbed you. You love being loved, and that's okay.
It's not okay when it starts affecting your mental health and general wellbeing, though. If you keep checking up on the people who have hurt you, you'll never get closure, you'll never heal, and you'll never fully move on. I'm not saying to forgive the people who have hurt you, because frankly, that's bullshit. If someone severely hurt you, don't you dare forgive them. What I am saying, though, is to quit stalking their Instagram.
Your wellbeing is more important than maintaining a friendship with someone who doesn't care about you anymore. You deserve more than the pain they caused you.
If a relationship ends poorly, you're usually expected to fix that. You can't have any harsh feelings lingering between you two so you can continue to mutually follow each other on Twitter without it being "weird." You "used to care about each other" so you need to repair back to that point but as friends.
It's bullshit.
Take care of yourself first. If a relationship was toxic, it makes no sense to keep that person in your life at all, on any level. You deserve to be okay, to be healthy, to be happy. You don't need to constantly see their face on your feed, wish them a happy birthday, and tell them you hope they're doing okay. You don't need to talk to them at all.
Quit checking up on people who have hurt you. You need to realize that your life has improved without them in it and accept that. It doesn't matter if you were friends before you dated or how great of a person they claim to be. It doesn't matter how they're doing, it matters how you're doing. Start putting yourself first.