I think if you have a "fairytale" view of relationships coupled with some possibly skewed ideas about what men (or women, SummerDad!) are like in the first place then that can put you in quite a vulnerable position in many ways.
If you're fixated on the idea of a relationship and believe that a good man/woman/relationship is rare and are worried about ending up alone, then you're likely to overlook small niggles which you might have at the beginning of a relationship, because you've already invested a lot in this and don't want to give it up and go back to that uncertain, single state wondering whether it's ever going to happen for you.
If you're lucky, you meet someone who's right for you anyway and everything is brilliant. In most cases, the relationship just isn't quite right and it all ends up going wrong because you try too hard to hang on to it anyway and you come out of it with your self esteem and self worth damaged. If you're really unlucky you find a controlling partner who at first seems amazing and promises this fairytale you have wanted forever, and turns into an utter living nightmare.
If you change your outlook about relationships, you're much more likely to end up in one which is right for you. Instead of seeing men as "naturally" XYZ (whatever your underlying beliefs about men are) just remember they're just as varied in outlook and opinions and beliefs as women are. Instead of feeling like most men are "bastards" and there are few "good" men around, just see it as that everyone is different and there are so many people in the world that there have to be a good few matches for everyone. Unfortunately there are some bastards 
but if you stop seeing it as "rare" to find a good man, then you won't be as gutted when someone comes along who is a perfectly good man but isn't a good match for you - you'll just think "Oh well. I'll find my match one day."
The other vitally important thing as BrandyButter says is to start looking inside for your sense of self worth. What makes you tick? Find something which makes you feel good about yourself, and do more of it. Get into a hobby or project, make plans for your future. Don't sit around and feel sad because you don't have someone to make plans with - make them for yourself! You can always change them if someone happens to come along - but if they're right for you, it's likely that your plans will go together quite nicely anyway. In any case the right partner wouldn't expect you to change your life plan for them.
The nice thing about all of this too is that you'll be so busy with all of your own things that you won't even want to bother with the timewasters, or people who you don't click with properly at first. You'll be more interested in getting on with your own stuff, so you are much less likely to end up in crappy relationships.