if you want happy memories- set it aside until you're in a happy mood to work on it. I keep a list handy of UFOs so I don't get too many, but I can work on things that come up in the meantime. Going back to a UFO gives you new energy to finish it. Who doesn't like picking up something already started- the end is that much closer.
(Spoken by the person with 8 UFOs on her list)