Self Doubt is a Mistake
The intellect gathers data from outside itself to make informed decisions.
If an individual (the ego) has never experienced its Universal Self, then the intellect will inform the ego, telling it what it is and what it isn't, what it can have and do, and what it can't have and do, based on data in the material world.
But when an individual experiences their Universal nature through meditation, a shift occurs. The ego interacts directly with Universality while the intellect takes a break so to speak.
In the waking state, the intellect tries to tell the individual that they are limited in some way but the individual knows better. They know themselves to be individual and Universal therefore creating a little disagreement between the intellect and the ego.
This internal conflict is temporary if one chooses to continue their twice daily meditation practice to experience Unity between individuality and Universality. In the waking state, they can pursue knowledge that supports the experience they are having in meditation and dismiss data that seems to contradict it.
The intellect is a strong and useful tool when it collects data in the material world which supports our full and complete Nature.
Self-doubt, feeling a lack of worthiness, fear of what others might think about us, fear of failure; this is all mistaken intellect. It is based only on that which changes day to day and fails to include the Truth of That which does not.
Recognition of mistaken intellect is a strong indication that we are on our way to self mastery. We note it, witness it, and take it as it comes.