Hey, you are not alone in your feelings. I am in exactly the same situation, but the cause of this is being a musician. So many people think they'd like to be friends and when I let them in eventually they become highly critical and become toxic. This is why I lead a predominantly lonely life.
Except what cynefin has shared is very good, and in a practical way we can look after ourselves, and in doing this we begin grabbing back some power to help us through our daily lives. I purposefully try not to look back at what was past, but stay in the present and remain close to my family of which I have a special sister who needs looking after. Devoting my time and energy to my church friends, all of them about my guardian's age helps to get me out of myself. And I love this self-care that cynefin talks about - it really does work.
You are always welcome to visit me. I like the anonymity here so that we can make good online friends, and this is a start. Also, try and do some self-care every day like I have begun since finishing a european tour with my band. Time to catch up in talking care of myself - and you, too.
Wishing you all the best,
~Belle