Perception

Depending on your perception certain things "become/are" real and certain things don't exist, that's where reality is perfectly fitted for you. As well as depending on your perception certain things "become/are" possible and certain things are impossible. That's abstract.
There's a reason why on the same single problem one person can see a certain solution while the other sees a different form of solution, and others may not see a solution at all. This is because with different perceptions come different solutions , meaning if you can't solve a problem it's not that the problem itself is unsolvable, it's just that you aren't comprehending the problem enough to perceive the solution.