I don't know if I've particularly talked about this here before, so I'll go ahead and sum up:
One of my core thoughts in relationships goes along these lines: If you can replace the words "But I love him/her" with "But I deserve to be treated like this," then clearly, there are issues with the relationship.
For example: Boyfriend is cheating on girl. She is unhappy, her self-confidence is a wreck. He either promises to change and doesn't, or basically blows her off with a "well, that's just how it is, baby. You can be with me on my terms, or not at all." She complains to me about it. I suggest that she find some backbone, self-respect, and LEAVE HIM. She says "But... but I LOVE HIM." (Translation: "I believe, deep down, that I DESERVE to be treated this way.")
I do, sometimes, give credence to the fact that you can't always control who you love. But I do believe - truly, and firmly - that what you DO about how you feel is UP TO YOU. You might love him. And he is treating you badly. HOWEVER, you control what you decide to do about it. If you decide that staying with him is the best option, that's YOUR CHOICE. No one else is forcing you to stay with him, be treated badly, continue to feel badly about yourself. (because we all know that in that sort of a relationship, the person on the 'being treated shabbily' end of things quickly stops asking 'what's wrong with him/her that she/he treats me this way' and ends up in the world of 'what's wrong with ME that I can't MAKE him/her act right?')
So, that's my core belief. And it applies to more than just boyfriend/girlfriend relationships. It applies to everything.
My father, for instance, tends to question my judgment a LOT. If there's a subject out there, chances are we disagree. And for a long time, we always ended up in nasty, hateful arguments. Seeing him stressed me out so badly that I'd be a wreck for weeks before we had our visit, and fumingly angry for days afterward. Eventually, I came to the conclusion that I had given him power over me, that I gave him the ability to make me crazy, and that I didn't have to do that.
Now, I'll give my father a lot of credit here: we talked about this, and we developed a much better relationship. The key to our relationship is the simple phrase: Do you want to fight about this? If he brings up something I feel strongly about (gay marriage, for instance, is a particularly contentious issue for us.) and it's the middle of Christmas dinner. "Do you want to fight about this?" "Well, no." "All right, then." It's a warning: I'm willing to fight about this issue if you are, but I'd prefer NOT to argue with you about it. We both know the other person isn't going to change their minds, and why disrupt the hell out of Christmas by being mad about stuff we can't do anything about ANYWAY.
I love my father. And I deserve to be treated with respect. He may not appreciate or agree with my beliefs, but he is required to respect my opinions.
And then the particularly hard part: I love myself. And I deserve this!
I deserve to have clothes that help me feel pretty. I deserve to not feel guilty about buying a dress, even if I only "need" to wear it once every few months. I deserve to spend money on myself. I deserve to be fit, and healthy. I deserve the pleasant ache in my shoulders after a yoga workout; I love myself enough to give myself that gift.
I love myself.
And I deserve to treat myself with respect.