Always Loosing Friends

So I have had a few years now where I've found longstanding friendships toxic or untenable and I'm beginning to wonder if some of it is my rigid sense of justice and not really understanding how people and conflict work. 

Examples:

Couple who wanted every plan to fit in with them and asked me to change a Halloween party date for them post invites going out. I decided this was unfriendly.

Old friend who always dropped me for new friends/partners.

Friend who forgot it was my birthday then told me I hadn't been considerate enough to her children with my choice of venue (I had already changed date and venue for them).

Couple who, when one got drunk and told me I couldn't be in love with my boyfriend because I make interactions so "scientific", tell me I'm blowing things out of proportion when I said I felt like I'd been betrayed and it had damaged my mental health and could they stop bringing it up. 

I realise coming from me these all seem very justified but I am aware there is a pattern of me not understanding why these wrong things keep happening and why it seems the norm to just move past it and that the onus is on me to carry on the friendship like normal? 

I am very confused but also know I can't just cut every person out because I haven't tried to understand how things work.