The original thought process and phrase comes from the general schools of thought shared by the famed Chinese general Sun-Tzu and the great Japanese swordsman Musashi.
It means one must train one's self to see (to consider while determining strategy and tactics)all things, whether large or small (important or unimportant) in proper perspective with reference to the battle or campaign at hand.
By doing so one cannot be taken in by what first appeared unimportant or non-threatening, nor fooled by that which at first appeared all important and surely the threat.
It is a lesson in seeking, attaining, then maintaining focus and balance so one will fight properly and thereby gain the victory.
Our eyes see only what is presented to them for view, which is easily manipulated and fooled by those in opposition to us.
The properly focused and balanced mind "sees" beyond physical vision and the tricks that can be played on it. Hence right strategy and right tactics regardless of what appears to be the truth. Therefore see (consider) large matters (things) as small, and small matters (things) as large in your mind. Don't let your eyes deceive you. Trust your planning, training, hard intelligence, and your capabilities. Apply right strategy with right tactics and employ a powerful Spirit at the right moment and you will succeed.
As conveyed to me by a little old Chinese gentleman who studied the arts of war at the feet of the masters.
And he was quite the swordsman, too
