How can I ignore my parents, while being in front of them?

I am speaking of giving them a silent treatment, which I have tried before and have caused a serious fight between me and them. Since that didn’t work, I want to be able to pretend that I am listening to them while being in front of them by nodding and agreeing. This is because they always criticize me and my life, others and their life, and they are extremely pessimistic. Is there any way I can pretend listening to them without actually listening to them? If I actually listen to what they say their words get stuck in my head and I start acting like their negative way. I am positive person and I want to live my life peacefully. I am getting sicker everyday if I actually listen to what they say all the time. Please someone help me out. I am really getting severe headaches and getting sick of them.