The pitfalls of being a wallflower

Sometimes I annoy myself. I'm not a super social person, especially if there are large groups of people involved, which means that sometimes I miss out on really fun things. Chvrches had a free show at a bar here in Chicago on Friday, and when I didn't get guaranteed entry tickets the night before, I opted to skip it rather than wait in line. Saturday, I didn't go play softball with my boyfriend and his friends because I'd just finished painting my nails, and didn't want the work to go to waste; apparently, it was an awesome time, and my nails were messed up by the next day anyway. Later on Saturday, I felt overwhelmed by the number of people at a backyard bonfire that I went to and decided to leave early. Again, a great time was had by most everyone else who was there.
I wouldn't really describe myself as shy, exactly. In most situations I can deal with people just fine. Every job that I've ever had has been customer service related, so time and practice have made it much easier for me to interact with people in a professional sort of framework. I'm also ok having one on one conversations, or conversations in small groups of people. Stick me in a room with 10 or 20 other people, though, and all I want to do is either hide in a corner with a book, or, better yet, leave. A significant amount of alcohol can help me get over that, but I don't really like to drink that much anymore, so I usually end up just going with my impulses.
It helps to have my boyfriend around to figuratively (and sometimes literally) hold my hand, bringing me into conversations and helping me feel included, without necessarily forcing me into heavy duty interaction with other people. While it's nice having that support, sometimes it also makes me feel guilty, like I'm keeping him from having fun by being too clingy or needy. He assures me that that's not the case, but it doesn't always keep me from thinking it.
I'm not happy about missing out on so many social activities this weekend, but there were still things that happened that I enjoyed. It was in the 70s for most of the weekend, so I spent a lot of time outdoors, walking around, reading, and checking out the autumn foliage.
Even though I missed the show on Friday, I got to take some nice outfit shots, and then I spent the evening with Brian, listening to records and playing Bioshock.
I also went shopping, and while I don't have any photos of the amazing vintage coat that I got for only $16 (it needs buttons and a cleaning), I do have a photo of the honking big nose ring that I really like, and am not sure I'll ever wear in real life.
I'm still going to enjoy my solitary pleasures a lot of the time, but I am going to make a little bit more of an effort to say yes to more social activities. I just need to get out of my bubble. Sometimes I forget that things like that can be fun, and this weekend felt like a wake up call for all the stuff that I'm missing out on.
So, what about you guys? Are you a social butterfly, or are you more likely to want to stay at home curled up with a good book? If you're more introverted, like me, how do you balance taking care of yourself with enjoying social activities with friends?