Doubt cannot come where there is a sense of closeness. Doubt needs 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 belonging, closeness, intimacy are all the antidotes for doubt.