I'm going to start out by saying this: our modern social media outlets are awesome. I've met some of my closest friends through them, and I can't even count the number of times I've been feeling down about my writing and gotten much-needed support through social media. I even wrote about my love of Twitter for writers a while back.
I also firmly believe it's important to take regular breaks from social media. For one thing, you won't get any writing done if you're spending all your time chatting about TV shows and news articles with your buddies. It's also easy to get discouraged and feel like you don't measure up if you're exposed to a constant stream of everyone else's greatest hits. And like many corners of the internet, the anonymity can sometimes bring out the worst in people.
This Huffington Post article lists some other signs (and includes some tips on how to accomplish the break).
Author Janice Hardy also has a good post here that explains why you should stop stressing and give yourself a pass to take it easy.
I've been on something of an enforced social media break since my son was born seven months ago. Now I'm feeling refreshed and ready to jump back into more active participation. But I'm going to keep an eye out for signs that I need a social-media time out.