I am so very sorry you are feeling so lonely and so hopeless to change it. It’s just true: All work and no play makes us dull and tired.
You are now in your 50s and tired. I get it. But 50 is not 100. You could still have a long life ahead. I think you can do things now to make the next decades better than the last ones.
You didn’t mention whether you have seen a therapist. If not, I hope you will. I don’t think you need to be working harder. I do think maybe you need to work smarter. Whatever you have been doing to solve your problems hasn’t worked – no matter how hard you have tried. A therapist may be able to give you new perspective on the situation and may be able to offer you the advice and support you need to be more successful in finding good friends.
You did say that you have a problem with relating to people your whole life. I suggest you take the quiz on the site for Autism/Aspergers.
It may be that you have a bit of Aspergers in your make-up that has handicapped you in the social world. Don’t let this idea worry you. If it is true, Aspergers is manageable. If it isn’t true, than you’ve just ruled it out as being the source of the problems.
I also suggest you see if there is a therapist in your area who offers group therapy. The advantage of group is that participants have a safe place where they can get feedback about how they are relating and they can get support for trying out new ways to relate. Look for a group that includes at least some people who are about the same age. Peers often share life experiences and cultural references that even wonderful young people just don’t “get”.
I know you are tired. But I hope you will follow through on these suggestions. I’d hate to think you will resign yourself to the way you feel now. You deserve better.
I wish you well.