Though you might have gotten along well at first, after a while you probably found it increasingly difficult to communicate with each other. Criticisms from your partner continue to stack up and create resentments, and could be depleting your self-esteem. As you've gotten to know each other better, you may have started to think that your partner is more prejudiced or conservative than you originally realized, and you want to challenge those limited ways of thinking.
They're equally hard on your ideas, and as time's gone on, they've establish a pattern of challenging your intellect more and more. They could think within themselves that you're smart and knowledgeable, but they project the feeling that they don't think you're very smart at all, or capable of making good decisions in life. What a limiting influence this could end up being! But it doesn't have to be limiting. In fact, you could use it as a chance to become more thorough in your thinking, more dedicated to your own path in life and your own ideas. The kind of challenges your lover presents to you require you to state your case and defend it. While this is likely tiresome and even annoying, it could prove an important part of your personal mental development. If, through this experience, you end up being a more effective communicator, then you'll have gotten something useful out of the tension that exists between you.