Everyone wants a relationship...though we define relationship in very different ways.
You know you want a relationship since you first catch yourself daydreaming about that special someone--guys do this too, trust me.
Then there's all sorts of relationships: romantic, platonic, frienships, work relationships, business relationships...even your relationship to the neighbors or the HOA.
So how do you know you're either in a bad relationship or you weren't meant to be in a relationship, or at least this one you're currently in? When you start losing your sense of self, when your standards go down, when you accept anything because it's better than nothing.
First, let's tackle the idea of sense of self. You should never lose yourself in anything you do, because finding yourself before getting back up for air at the end is a biatch.
Second, don't ever let your standards go down, unless you have unrealistic standards--in which case you need to re-evaluate and correct where needed. Letting your standards go down brings your morale down, and this is not acceptable my friend.
Finally, something bad IS NOT better than nothing. Nothing is a big empty void that you can fill with anything, such as a fantastic sense of self-esteem at accomplishing great things that turn you on and up. Or, you can fill the great vast emptiness of "What could be" with a crappy relationship? So when you put it this way, is it REALLY better to be putting up with a bad relationship, bad job, bad relatives, bad whatever...when you could really be creating and moving into a space that you've shaped yourself?
Never say you can't do something, there's nothing you can't do if you put your mind to it. Then again, if you plan for nothing, you achieve it.