Once you have what you think is your final solution, don't implement it immediately. The goal here is to take some time to distance yourself a bit from your work so that you can look at it more objectively and holistically.

Investing a lot of energy into an answer can affect your judgement and make you lose perspective (possibly because of an emotional investment in something you've worked hard on, or because you focused on details for so long that you lost track of the big picture).

I've heard more than once about writers doing this; putting a manuscript in a drawer and re-reading it X weeks/months later, with "fresh eyes". I think it can apply to other fields as well.