In mathematics there are two kinds of optimums. There is the global optimum which is the best and most perfect solution. Then there is the local optimum. The local optimum is the greatest solution in its immediate vicinity. It is not the best solution that exists in the problem space but any step away from it would be in a downward direction. Once one of these is reached optimization plateaus. The great solution is never found because to get there would mean the abandonment of the good enough. Good can be the enemy of great.