It has been said that many cynics were once great optimists. They were once full of hope and optimism, but after too many disappointments, or perhaps one large disappointment, all that hope and optimism was drained and was replaced by pessimism and cynicism. I think Zechariah, the father of John the Baptist, may have been such a person.
It has been my experience that most of the Christian life takes place in the wilderness, not the Promised Land. That is, it is much more common to be struggling (spiritually) in one form or another or to one degree or another than it is to be sitting back and relaxing. One of the reasons for this is that spiritual growth requires work and effort, which means there will likely be a lot of struggling and failing. Another, and often overlooked reason I think, is injustice. Times when God does not do what he has promised to do.