There are a few things I haven't tried yet. Maybe we haven't flown our own plane yet, or lived in a cave in the Himalayas or sailed around the world, or written that best-selling novel. All of these are splendid things to do in the world except they are a waste of time and energy. Sceptical doubt makes itself felt when one isn't quite sure what one's next move should be. One hasn't found a direction yet.
Sceptical doubt is the fetter in the mind when the clarity which comes from a path moment is absent.
The consciousness arising at that time removes all doubt, because one has experienced the proof oneself. When we bite into the mango, we know its taste. The wrong view of self is the most damaging fetter that besets the ordinary person. This wrong view of self is the cause of all problems that could possibly arise. Wrong view of self is the root which generates all subsequent pain, grief and lamentation.