You may read this and think, "I've never dated anyone who is married or with another women." I thought the same thing, but then read this lesson and learned that that isn't the only way men are unavailable.
Men can be unavailable by being married, having a girlfriend (even if they swear they are going to break up soon), having a boyfriend, by telling you they can't commit, by continuously dump you, by cheating on you, or by having any kinda of unresolved substance abuse.
You live and you learn, but the most important part of this is to understand that your time is precious and you deserve to have something better than this in your life.
One exercise to help you with this (as suggested by our fabulous authors) is to right a letter to Mr. Unavailable, telling him how you truly feel. I usually do this when I'm angry and don't want to blurt out something I'll regret saying later. But this exercise is meant to help you put down what you feel on paper (or in an email). You may be surprised by what you say.