Life moves in cycles that are at different frequencies. When they all end up on a peak or trough at the same time, it is trying to tell you something. Listen, and then move, based on your own interpretation of what you want to hear.

In this case, it sounds like you have a project you want to get done. Get it done. Then go on to something new. If you have a PHB kill the project, or otherwise remove your delight in it, use that as the catalyst to move on.

Or, if you wake up one morning realizing that you have to do that startup right now then do it.