There is a further point. In the case of my own boy, and presumably in other cases too, the experience of overcoming fear is extraordinarily delightful. It is easy to rouse the boy’s pride: when he has won praise for courage, he is radiantly happy for the rest of the day. At a later stage, a timid boy suffers agonies through the contempt of other boys, and it is much more difficult then for him to acquire new habits. I think, therefore, that the early acquisition of self-control in the matter of fear, and the early teaching of physical enterprise, are of sufficient importance to warrant somewhat drastic methods.
Source: On Education, especially in early childhood, 1926, Pt. 2：Education of character, chap. 4: Fear.
More info.:http://russell-j.com/beginner/OE04-070.HTM