First off, I find it's often best for me to stand away from the piece I view as not up to par, as it were. Sometimes, leaving it alone overnight and re-reading it with fresh eyes can do a lot for the perspective. You may find there are things worth salvaging. Secondly, you may wish to play your game for a bit. Let your Sims be themselves and see if that doesn't inspire something. Or take a slight break and watch a movie. What I'm suggesting, which is often true for myself, is I get into a mood wherein nothing is good. It could be great, but I am incapable of seeing it. This is not the time to throw the piece out, by any means. Also, sometimes, in the morning, I'll get a line or two of dialogue that takes the update/chapter I was trying to write in a whole different direction. I may grab a description or two from the ill-fated update, but I let the new inspiration have full reign.
As for the battle against Writer's Block, allow yourself to act on the inspiration. Jot down that thought, that bit of dialogue. Give your subconscious mind permission to get creative. If you keep ignoring it, that's when you run into trouble. I know, I suffered and eight-year bout of Writer's Block. I got to the point where I thought I would never write again.
Hope this helps, even a little. Oh, and be kind to yourself.