This is more, as you said, concentration practice; and we don't encourage these types of practices. We prefer you to watch the breathing as it is, and see the arising and passing of the fears, etc. and to develop confidence through wise reflection, through letting go of one's fears by seeing how they affect the body and the mind, through Insight into Cause and Effect, through understanding Dukkha and the cause of it, through developing compassion for oneself and letting go; these types of ways rather than concentration practices.
If there is a tendency for a lot of restlessness and agitation in the mind, I sometimes feel it is ok to note, "Just one breath at the time", these kinds of words just to calm the mind down, but then to let these types of practice go and come back to the insight practice and look at especially the Five Hindrances at appropriate times. When the fear arises, to learn to balance the wrong view at the time that we are trying to let go of it and then come back to observing the mind/body process.
In regards to developing confidence, there are the confidence inspiring objects of meditation that we teach. So we don't just have to tell ourselves to develop confidence, we can actually start to chip at the wrong view and the doubts that prevent us from having confidence.