In The Art of Money Getting, P.T. Barnum Wrote:

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 became 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.

Now, I’m no hunter, but I know this: If you wanted to hunt a buffalo, you wouldn’t use a shotgun. A shotgun shoots a number of tiny metal balls that spread out. This makes it much easier to hit what you are aiming for. That works great for small things, ducks, clay pigeons and the like. Buffalo are tough, though, and if you shot it with a shotgun, you would only succeed in angering the animal. You need a high powered rifle, which focuses all its energy in one bullet.

The sun puts out a tremendous amount of energy, but no matter how dry the wood is, just setting it in the sun will never start a fire. Alone the sun may burn your skin, warm your water or dry up your garden, but it will never be enough to light a candle. However, when focused even with a small magnifying glass, the sun will almost instantly produce smoke, and soon fire.

Just like the buffalo and the fire, your goals require focus. Focus makes success possible. When you are striving to reach a big goal, your energies must be focused. Spreading out your time and effort among too many goals is a waste. Just pick one goal and concentrate on it. Keep concentrating until you have achieved. You will get it soon enough, and then you can work on your next goal.

I believe there is an Irish proverb that sums it up best, “If you want to do many things, do them, one at a time.”