I am like a social introvert. I feel like it is taking care of myself when we have friends over. It's like meeting everyone's needs but also making my life interesting and fun. We have hosted poker nights, halloween parties, basic holiday gatherings or had friends over for pizza and conversation (and sometimes we go to friends' houses, too). We joke that are parties are kid friendly adult parties because we make sure we have juice boxes and everything for the kids, but they socialize and the adults socialize. It's fun because *I* get a chance to chat with my friends and play some fun games (we love board games and poker). There's always kids running around so it's my children's chance to see friends and have a blast, too. To make it cheaper, we usually have gatherings potluck style to minimize my preparation. My kids are older, though, and I do remember one poker night YEARS ago that we hosted when DD1 was a colicky baby. I literally spent the whole night in the back room bedroom, rocking a screaming baby. Luckily she outgrew it!
Other ways I take care of myself are the obvious ones- coffee with a friend, getting my hair done professionally (it's a splurge but worth it and my husband encourages me to do it because it makes me feel good), I paint my own nails cheesy crazy colors sometimes, I am a gym member and go work out and sit in the sauna/steam room, I read great books on my kindle, I go for walks. One simple thing I do is my afternoon cup of coffee with a piece of good chocolate. I have a stash of chocolate no one else gets and I eat a piece everyday as part of my daily routine. It's really not the quantity of stuff you do or how often it happens, it the quality of what you do. I don't mean in a monetary sense. But those little things, like painting my nails with dorky, glittery colors, makes me feel happy every time I look at them. And that piece of chocolate and coffee happens right before my kids are home from school so it's like that last bit of quiet before the rush of dinner/homework/etc happens. It's the little things. Sometimes I meditate and my cats sit near me and the dog curls up next to me and it's very peaceful and very much for myself. But it also benefits everyone because I feel more balanced.
I am not big on mom's nights out, though that's a suggestion. I like going out with my husband so if I'm going to go out, I want him along. But my son is old enough to stay with my youngers, now. When they were tiny and we didn't have a babysitter, I did do occasional mom's night out, though. I don't know how old your kids are.
I am not probably not really considered a SAHM anymore. I work part time from home and go to online college. BUT I still really see myself as a SAHM because I am home and my part time money really only pays for a couple of the kids' extracurricular activities. For a long time I felt kind of guilty for being able to meet a friend for coffee or doing stuff in the middle of the day. Sometimes I feel weird being home, even working and with college, while my kids are in school. But now, instead of feeling guilty for being home, I feel grateful towards my husband for working in a career that allows me to stay home and he encourages and supports me in whatever I choose to do (I did work full time out of the home briefly and quit because I hated it). Over the years, it has become easier to do things for myself.. to the extent that I will now ask if someone wants to come to Target or the grocery store with me because I want the company! heehee