Details become expensive when discovered late.

Fixing a detail while the work is still open costs a few minutes. Fixing the same detail after everything has been built on top of it means unpicking decisions, redoing dependent work, and often explaining to people who had already moved on. The problem did not grow, the surrounding structure did, and it now has to be disturbed.

When you spot something small and unfinished and think you will come back to it, weigh that against what it will cost later. Often the honest choice is to deal with it now while it is still cheap. If you truly cannot, write it down somewhere it will survive your memory.