I don't know why people love ordered things so much but they really do. They hate randomness.Finding pattern in the things is really a fascinating job,but we can not do it in all the cases,like in case of prime numbers.
  In combinatorics we do the same thing we first find out pattern in cases and try to find out a general rule and count things now often you do mistakes if your patterns do interact ,what I mean to say that there is a intersection and you do not notice it. What is best about combinatorics that we don't have to remember everything, you could find a new pattern everywhere so you have to discover it instantaneously.As many problems you see as early you will understand this.

                           
   I have decided that each day I spend 2 hours for combinatorics in my day's work and see that my performance will improve or not.Sometimes it needs so much common sense that I don't have, why I don't know, may be I am too stupid.But who cares :-) many things I was not but I am now likewise logical power and common sense will also come.