The exact process you use to build courage isn't important. What's important is that you consciously do it. Just as your muscles will atrophy if you don't regularly stress them, your courage will atrophy if you don't consistently challenge yourself to face down your fears. In the absence of this kind of conscious conditioning, you'll automatically become weak in both body and mind. If you aren't regularly exercising your courage, then you are strengthening your fear by default; there is no middle ground.