Doubt cannot come where there is a sense of closeness. Doubt needs a distance to appear. You never doubt something that is dear to you, close to you.

The moment you doubt, it is no longer dear to you; a distance has come.

You may doubt yourself, but you do not doubt that which is yours.

Self-doubt is a lack of closeness to oneself, a sense of belongingness, closeness, initmacy are all the antidotes for doubt.