Just don't let all her criticism wear you down. Stand up for yourself and what you believe in. Sometimes you will be wrong, and it's okay to admit that. And sometimes you may end up letting go of an argument just to keep the peace. That's okay, too. But if you surrender every time she criticizes you, she won't respect you anymore, and you won't have much self-esteem left. Ultimately, you might be happier with someone who is more supportive and less judgmental.
Good decisions come from experience. Experience comes from bad decisions.