The missing puzzle piece changes every glance at the completed portion.

One gap changes the whole. Everything else is complete and correct, and the eye goes to the hole anyway, so the finished area is now experienced as a setting for what is not there. A single absence can reorganize your perception of everything present.

Notice when this is happening to you: a good year read through one loss, a strong piece of work seen only through its flaw, a person summarised by the thing they cannot do. The missing part is real and it is not the whole picture. Deliberately naming what is present, out loud, is a way of restoring proportion.