I have the opposite problem. Too many UFOs. Makes for a very disorganized (clever word for messy) sewing room. Trying to clean it up now and making a "to be finished" pile. Hopefully, I will finish this pile before starting on anything else with a final goal of no more than two projects at a time.
Maybe you could expand your one at a time limit to two. Then you could bounce between them when you feel like you've hit a roadblock.