Argh!

Why is it that whenever I sit down to write something, I get writers wall? I have been trying to write a commentary on Ibsen's Hedda Gabler, I know what I want to say and I can't get it out. I'm also trying to quit smoking and the only thing that is going through my head is "I want a cigarette" DH is also trying to quit, and we had a huge fight this morning. So what do I do? I get cigarettes, and now I hate myself for it. It's one of those head banging against a wall problems.