Engage in one kind of business only, and stick to it faithfully until
you succeed, or until your experience shows that you should abandon it.
A constant hammering on one nail will generally drive it home at last,
so that it can be clinched. When a man's undivided attention is centered
on one object, his mind will constantly be suggesting improvements
of value, which would escape him if his brain was occupied by a dozen
different subjects at once. Many a fortune has slipped through a man's
fingers because he was engaged in too many occupations at a time. There
is good sense in the old caution against having too many irons in the
fire at once.