Yes, the other fellows give good advice about taking a break if you need it. If you are biking for fun, why do it if it is not fun?
However, if you are training, then the slumps are a great opportunity to excel. I tell my martial arts students that when they train on the days they least want to train - the days that they want to stay home and watch television reruns - that is the day they will break through the training ceiling where they may have reached a plateau.
So, if you are in training, take advantage of the slump. It is the test that separates the winners from the losers.