Know your why for a project before the boring middle hits. The why is what carries you through.

Every project has a stretch where the novelty is gone and the end is not close, and enthusiasm does not survive it unaided. A reason you decided on at the start, written down, is what gets you across, because in the middle you will not be able to produce one. Most abandoned work was not beyond the person’s ability. It simply ran out of fuel somewhere near the midpoint.

Write one sentence on why this project matters to you and keep it where you work. Make it specific rather than noble. Read it on the day you want to quit, and give it one more session.