A small child who looks at some big monkey bars and feels doubt or caution is simply intelligent. Doubt is just one assessment of a situation.
Shame is the bigger issue. People who are ashamed of displaying doubt have a dilemma – like because then a bunch of new agers might bash them with guilt about not enough “positive thinking.”
The one who has the courage to welcome doubt is brave. The one who has the courage to welcome shame is humble as well as brave.
The one who is already humble has no fear of being humiliated. That is why the humble can be so much more powerful than those who are trying to defend their ego and protect it from humiliation.
ADDITIONAL COMMENTS ADDED LATER:
Consider the idea that “I wish that I never had any self-doubt, especially not now, so why do I have it?” It can be asked in two very different ways. One is simple and curious. It is actually interested in what is meant by “self-doubting.” It is open to learning.
The other way to ask the question is the activity of agonizing (a shameful doubting of one’s self). There may be a sense of rejection (self-rejection).
We can project that on others, sometimes in very “immature” ways: “Robin Williams should not have had any self doubt ever and, because of his negative sins of having self-doubt, we must all ridicule him for being a shame upon humanity.”
There is no learning in progress in that case. There is no curiosity, but only terror and shame. There is a fixation on a particular opinion as “a certainty” (which can be labeled arrogance or fanaticism or idolatry).