Even a nod from a person who is esteemed is of more force than a thousand arguments or studied sentences from others.

Approval from someone you respect carries a weight no amount of reasoning from a stranger will match. That is not entirely rational, and it is how people are, since we take our bearings from a small number of others whose judgement we trust. It also means a brief word from the right person can change what someone believes about themselves.

You are that person to somebody, so use it deliberately. Say the specific approving thing to the person who would value it, rather than assuming they know. Ten words from you may do more than an afternoon of anyone else’s encouragement.