You've racked your mind but the solution to your problem is still incomprehensible. You know you should be able to solve the problem, yet you cannot. Such problems can range from an abstract math question, deciphering statutory language, or something more mundane like remembering your former colleague’s name.
Problem Solving Through Incubation
Empirical evidence suggests that incubation can be a wise strategy for solving your problem. 
The process whereby a problem is consciously ignored for a while after which the unconscious offers a solution.
The Role of Distraction
Incubation is seen as fruitful because one is distracted from the problem at hand. Not thinking about a problem for a while may lead people to forget wrong heuristics or inappropriate strategies in general. Distraction, then allows people to give the problem a fresh look.
So next time you’re stuck on a seemingly incomprehensible problem, distract yourself. Take a short walk, then return to face the problem with a fresh look.