One of the most commonly believed misconceptions is that we are supposed to be happy, all the time. We think that sadness is something that needs to be cured, as if it was a disease. Many of us strive to live a life free from judgment, yet we harshly judge one emotional state over another.
Feeling sad, angry, or even just plain bored are perfectly acceptable states of being. If you feel sad, be with the sadness without judging it as negative. It isn't negative unless you think it is. It's simply a reaction to life. Trust life to take you where you are meant to be.