From one of Wayne Dyer's CDs, which he did along with Byron Katie, I heard a similar question. The questioner expressed disappointment at not being able to maintain the "high" that she initially experienced after her introduction to personal development and the law of attraction. She was worried that she had "failed." Dr. Dyer's very reassuring response was that while we are inhabiting our physical body and living in this physical reality, such is life. There will always be ups and downs. He experiences them. Byron Katie experiences them. Everyone does.
I don't think the problem is so much the down periods as much as how you handle the down times. My response to a period of being down, be it either encountering serious difficulties or just "feeling low," is to acknowledge that I'm in a down period, but to not dwell on it. Just as surely as I know I'm in a valley, I know that another mountain top is just ahead
