Quitting a bad plan early is cheaper than finishing it just to prove you were right.

Finishing something broken to protect your reputation is the most expensive kind of pride. Every extra week costs the same hours a working plan would have taken, with none of the result, and the people watching are rarely as impressed by persistence as you imagine. Stopping early looks like failure and is usually just arithmetic. Whether to continue should be decided from here, not from what you announced in September.

Pick the thing you are continuing mainly so as not to look wrong. Ask what the remaining cost buys you. If the honest answer is nothing, stop this week and say so plainly.