He must classify and arrange; but, after he has done all that he can, he must still expect that his daily business will continue to consist of a vast multitude of minute particulars, from one to another of which the mind must turn with a rapidity which few of the other employments of life ever demand.
These are the essential sources of difficulty with which the teacher has to contend; but, as I shall endeavor to show in succeeding chapters, though they can not be entirely removed, they can be so far mitigated by the appropriate means as to render the employment a happy one.

I have thought it best, however, as this work will doubtless be read by many who, when they read it, are yet to begin their labors, to describe frankly and fully to them the difficulties which beset the path they are about to enter.

"The wisdom of the prudent is to understand his way." It is often wisdom to understand it beforehand..