You've done this sort of labor before, now do it again. One day at a time. Meet your daily goal, and then put a CD on and fire up a pizza. Day by day. You can do it.
Writing is cumulative.
You write a few pages a day and keep going and eventually you get there. Dear Mr. Blue, Several months ago I met a wonderful man and we began dating. He had recently ended a relationship and was cautious about appearing to be on the rebound. We enjoyed each other's company immensely, but did not sleep together. A month later, I began dating another man.