It sounds like you are maybe grieving a little for what might have been, I'd say that's fine to acknowledge you feel that and those are valid emotions you are experiencing. It's okay to feel sad sometimes, as long as it doesn't take over your life.

Why do you feel that you will be only left with 'awful men' however? I know some nice guys who are still single too in your age bracket, you might just meet someone who is worth the wait. Likewise your friend's marriage is as others have pointed out no guarantee of happiness, and facebook is a highly edited view of peoples lives, the reality is likely to be quite different (and not shared!).