The wrong thread can make careful work fail at the smallest point.

A whole piece of work is only as sound as its least considered component. Hours of careful cutting and fitting can be undone by thread that was chosen without thinking, and the failure will show up at a seam rather than anywhere you were concentrating. Attention naturally goes to the difficult parts, which is exactly why the trivial ones are where things give way. The small decision made quickly is the one to check.

Look at whatever you are building and find the component you chose without thought. Upgrading the cheapest, least interesting part is usually the highest return available for the effort.