I think that living with the sort of issues that fibro causes (whether it's fibro or not) causes us to evaluate what is important to us. Our free time is very precious to us, so I don't see any point in wasting it on anyone that I would say causes me undue stress, or adds extra baggage.
I've found, since this all started, that I don't go out nearly as much as I used to, but I still manage to get out to sing karaoke now and then. I don't drink as often as I used to because I've found that even one drink that I have when I'm not feeling 100% can trigger either my anxiety, or a host of pain and lethargy the next day, and not in the normal hang-over way. Sometimes, though, I let myself if I feel strong, and at those times I don't usually have any bad reactions.
I feel that I am lucky because the friends I had before all of this set in are pretty much the same group of friends that I have now. The lion's share of them have always been very supportive and inquisitive, and have also gone out of their way to bring the functions to me. They've also gone out of their way to choose things to do that I'm more willing to try on a bad day, like board game parties and such, and never give me flak if I have to cancel at the last minute. Without my friends I feel that I'd be a great candidate for depression, but with their help I've managed to keep it off my list of symptoms.
I was scared to death of trying to date after my ex and I split up, but last year in September I joined a D and D group that some friends of mine are in, and since December I've been dating the DM (I won't bore you with how the game works, lol). He has been incredibly supportive, and has probably done as much research on what to expect from fibro in the past 3 months as I have in the entire time I've been diagnosed >XD
I think the key with social interactions is to make sure you have a supportive network of people that you trust with sharing your diagnosis and who accept your limitations, and to always forgive yourself and not feel as though you are a burden. Past that, doing whatever YOU feel comfortable doing is the key. If you wanna stay in, stay in! If you wanna try to go out, go out! You can always leave early if it's a failure, but if you are a "social butterfly" like I've always been not going out for fear of... anything... can end up leading to some negative thinking patterns.
All of that being said, I'd like to stress that I do not think that everyone needs to be social. I just feel that everyone should search for ways to accommodate their own desires.