I can look at my own welds and see the obvious problems. It's the ones hiding inside that keep me up. A flaw under the surface that looks perfect on top but could fail under load, and I signed off on it. I keep going back over the scans, second-guessing what I can't quite see.
More people experience this than they realize.
You can inspect your work, but catching the flaws hidden inside still eludes you.
If this sounds familiar, the Library can help you find the bigger picture.