Beating myself up?

So me and my partner have been talking about anal for a few months. I’ve been hesitant cuz I was always against it. But agreed cuz I wanted to try it and I know how much he wants it.Well he got in a little last month after a night of drinking. I told him he needed to bring lube. Well tonight he did and I couldn’t do it. He tried to loosen me up back there and it wasn’t working. Then I was getting in my own head about not being able to perform for him. So we called it quits for the night. Before he left we sex and we were fine. I told him that as a woman I wanna do this for him but I can’t get myself to relax. He said well we can keep trying. I wanna do it for him but what if I don’t enjoy it? Do I keep trying are there any tips that can help me? Idk what to do?