I have written in the past about how happiness is fleeting, and joy is enduring. Happiness by definition calls for something to happen on the outside for the happy feeling to be experienced. Joy needs no external stimuli for it to be experienced. 
There are good days and not so good days. When you experience a not so good day, always remember that you can find joy in the journey towards your destination. All human beings are designed to yearn for something more, for better, for growth. If you were not yearning for something more, you would not be reading this.
Joy is found in the journey towards better, not necessarily in the bettering. “Following your bliss” always provides more fulfillment and pleasure than “reaching your bliss.” There is no guarantee that the journey will be pleasant, but the unpleasantries are meant to make your story better, not to distract you from the joy of the journey. Contrast provides clarity. The more you are exposed to things you don’t want for yourself, the more clear you are about exactly what you want for yourself.
No matter what dark valleys you have to go through as you follow your bliss, remember that joy is always in your gratitude for the journey.