Fortunately I always seem to have too much I want to write and not enough time to write it! When I get to a difficult plot point or piece of action, I often leave that part for a couple of days and just think about it when I'm doing something completely different. The answer often then just comes to me. If I am really stuck, I force myself to just write something. I can always tidy it up or change it later. Asking my children what they would write next also gives me ideas.