The Problem with Painting

Several months ago I noticed that the little section of wall by my computer was dirty and needed a fresh coat of paint.  So I got out the paint and painting paraphenalia and painted it.  Looks clean and fresh.  Good job, Florence!!  Oh wait, the wall next to it looks awful!  How did that happen?  It looked fine until I painted the first wall.  OK, out comes the paint and paraphenalia and once again, Good job! Looks gr....Oh no, the next wall looks grungy.  Why did I ever start this when I could have just taken my glasses off and not noticed the first wall??