I am bothered by the failure rate. When we're talking about life and death, either physical or spiritual, numbers matter! Every number is a person. However, if I focus more on the failures, then I'm going to fear failure every time I lay hands on someone. If I focus more on the success I'm going to grow in faith and expectation. ...
Focusing on the hits while ignoring the misses is a good way to convince oneself of a belief, and I suppose that "to grow in faith and expectation" is an accurate, even if somewhat euphemistic, description of that. The problem is that this method can work as well for a false belief as for a true one. If "to grow in faith and expectation" is your sole goal, convinced that the belief in and of itself is good, then you have the right approach for achieving that goal.
I think that this underscores a very fundamental difference between religious thought and skeptical thought. It seems to me that the religious are primarily concerned with whether a belief is good (feels morally right, brings comfort, encourages good behavior, etc.), while the skeptic is primarily concerned with whether a belief is true.
It seems to me that what motivates believers of pretty much any religion is not their belief in gods, but rather a belief in belief.