How do I let go of the resentment?

[JJRJ1002]

So many of my friends have shit on me over the years so now I'm left with no friends. It has knocked my confidence in friendship a lot because these were people that I thought I'd be friends for life with.

A few years ago my best friend of 20 years stopped talking to me because I called her boyfriend an idiot for cheating on her. By stopping talking to me she also took away my social circle. So I was left with no one. I was totally devastated .
It took me years to feel 'over it'
I had a folder of hers that she had left in my house with a few sentimental items in it and a few months ago I thought I'd msg her to see if she wanted to pick it up. She didn't reply for a few days then replied saying she would come and get it. Which she did and when she picked it up she ended up spending the day at my house chatting about all her friends and everything she has been up to, all the places she's gone etc etc. Then when she left I felt a sudden HUGE amount of anger that I was so stupid to have got myself into the position of feeling like I missed her and wanted her back in my life and the HUGE resentment at the fact that she had all these friends that she could go out and do things with and I had no one. I was also very upset that she didn't feel like she had to mention everything that happened years ago as I had been longing for an apology.

How do I let go of these feelings? I hate feeling consumed by sadness and resentment again over her when I had been doing well for so long

I'm so sorry to hear about how your ex friend has treated you, and that she took away your social circle. I don't blame you for still feeling angry and resentful towards her, I know I would too!

I think in your situation I would focus on trying to find new friends and acquaintances, basically stick two fingers up at her as you don't need her friendship nor the friendships of the sheep that dropped you on her say so!

They're not 'friends', though are they OP? Then or now.
I think you deserve better.

I'm so mad at myself for doing the nice thing and seeing if she wanted to pick up her stuff because she has brought me right back to where I was at the beginning and felt she wanted to mug me off by bragging about her wonderful life with her wonderful friends

You've had a set back.
However, now she has collected her belongings, you can move on in the knowledge that you never have to speak to her or see her again.
I wouldn't want to be friends with someone who found it so easy to drop their friends. Out of interest, is she still with the cheating slimeball?

No they are not together anymore (she didn't tell me this, I seen on Facebook)

Giving her the opportunity to collect her folder was a nice gesture, however letting her spend a whole day at your house bragging about her life, was just plain weird. You've surrendered far too much power to this woman and despite her past behaviour, you continued the dynamic by letting her stay and brag.

Looking to this woman to validate your past and present feelings is futile. How do you get past the resentment? By accepting that she wasn't and still isn't a friend and that she doesn't have magic powers. What happened in the past was shitty but building into this massive injustice only serves to reinforces your victimhood.