Be temperate in eating your food, drinking cold water, taking exposure, in your hours and in general.  For example, it is not a good plan to have too much of anything which you like particularly.  It immediately dulls the sense of pleasure in that thing, and, raising the level of your likes to a degree that makes you dislike some other thing, perhaps, which you liked before, thus working a loss rather than a gain.  Therefore, temperance, which is synonymous of moderation, in my use of the word, is the wisest thing you can practise.  But be intemperate in the pursuit of your object.  Let no expense be too large to equip yourself physically or mentally for your life’s work, as, for example, to assure regular exercise, to cure any physical imperfection or disease, or for the furtherance of any desire for investigation on natural or scientific subjects or points of interest allied to the thing which you are seeking to attain.  There is no need of moderation in labor, exposure, or discomfort.  Thus you will eventually reach your ends, and may obtain results at which people will stand amazed, believing them to be beyond the range of possibilities, as they will not know that for years a systematic preparation has been going on to prepare yourself for this result.

As a boy, your desires have been limited by your opportunities.  You have had certain kinds of recreation provided for you which you have enjoyed.  Your expenditure of money has been limited by your purse, which will have been small if your parents were wise; and your expenditure of time will have been limited by the hours you have been unable to take from study, which will also have been small.

At college your opportunities will have broadened, and you begin to have something similar to the elective system.  You can choose more freely how to spend your time.  Your development to this point, I have already said, may be called the rounding of the handle; and your education will be normal if you have average application, intelligence, and memory.  During college your future course will begin to shape itself, but before you fix upon your definite object there is likely to be a period at which you can be tempted into the greatest dissipation.  By dissipation I do not mean the accepted term, but the scientific use of the word; namely, the useless expenditure of energy in futile pursuits.  It is the opposite of concentration, which means directing energy upon your object.  To make myself clearer, I will define energy as also meaning, in addition to your labor, your money, as money is the accumulated energy of your ancestors, just as coal is the accumulated energy of sunshine.