When do you let the past go?

I love facebook, ok, maybe I don't. For some reason I'm having a moment of contemplation, I'm wondering about my past. Before the current life, before the girls, the man, and the house in the 'burbs, so should I just let it go and be happy?
I looked up a friend. Sure she was a friend of a life past, a former bridesmaid in fact. She was at my first wedding, years ago, and since then she split, left town, I split, left town, got divorced etc and have the happy life I have now. Why then or what possessed me to google or search facebook for a name I remembered. I found her, she'd gotten married and had a child. She also had listed on her facebook page my ex. And while I don't hate him, I don't have any real desire to see him, chat to him or even throw rotten eggs at him from afar. Maybe I just don't really care for him hearing how my life is going. Maybe I'm old enough, or moved on enough to be over the stuff from the past and not care.
I care about her, and I care about the other person I looked up. And messaged. Crap, this is almost as bad as texting. What if she responds? What made me want to look up the past and make some contact? Why these days am I thinking more and more about the years before now? Will it hurt any of the current players in my life, or is it just some frivilous curiousity of people past?
I'm nervous and excited to see if either girl responds. Hell, I text frequently the girl who would have been my sister-in-law of sorts if I'd stayed in that past life. Just makes me realise that some people don't care about what has gone before and instead value the friendships they had. Or the friendships they do have now, regardless of water under the bridge.

Either way, it's late, there is snoring from the couch and I have 2 angels to check on.
The past may be out there, but the present is under this roof.