The world is full of people who are "almost a success." They stop just this side of success.

Their courage oozes out just before they become expert.

How many of us have acquisitions which remain permanently unavailable because not carried quite to the point of skill?
How many people "almost know a language or two," which they can neither write nor speak; a science or two whose elements they have not quite acquired; an art or two partially mastered, but which they can not practice with satisfaction or profit! The habit of desultoriness, which has been acquired by allowing yourself to abandon a half-finished work, more than balances any little skill gained in one vocation which might possibly be of use later.
Beware of that frequently fatal gift, versatility.

Many a person misses being a great man by splitting into two middling ones.
Universality is the _ignis fatuus_ which has deluded to ruin many a promising mind.

In attempting to gain a knowledge of half a hundred subjects it has mastered none.