It's good to correct your mistakes when you notice them.
Alex is painting a room and notices he missed a spot on another wall while he is painting.
Alex wants to finish painting.
Alex decides to fix the spot while the paint is wet.
Alex decides to finish the rest of the painting before going back to fix the spot.
The spot is covered up and the room looks great when he is done.
Alex forgets to fix the spot before he is done and the touchup is very noticeable.