A good first step is to just notice when you are being attracted to or getting involved with men who are not available. Maybe you don't notice right away, as you suggested. That's okay. You notice when you notice.

When you do notice, don't judge yourself. Think along the lines of sighing gently and saying to yourself Oh, there it is again. . When you notice without judging yourself, you allow your mind a chance to handle things differently than in the past. In a way, it is like trying to correct a bad habit. It takes time and patience with yourself. Be gentle with yourself and allow your mind a chance to figure out new ways of being.