But while it is not true that we fail to practice a thing merely because we fail to remember it, it is true that if we do not practice we are not very likely to remember it. The only way we could remember would be by constant re-reading, for knowledge unused tends to drop out of mind. Knowledge used does not need to be remembered; practice forms habits and habits make memory unnecessary. The rule is nothing; the application is everything. Practice being the thing needful, it is essential that we put aside a certain amount of time for it. Unless you lay out a definite program, unless you put aside, say, one-half hour every day, for pure downright independent thinking, you will probably neglect to practice at all. One-half hour out of every twenty-four seems little enough. You may think you can fit it in with no trouble. But no matter how shamelessly you have been putting in your time, you have been doing _something_ with it. In order to get in your thirty minutes of thinking, you will have to put aside something which has been habitually taking up a half hour of your day. You cannot expect simply to add thinking to your other activities. Some other activity must be cut down or cut out.[24] You may think me quite lenient in advising only one-half hour a day. You may even go so far as to say that one-half hour a day is not enough. Perhaps it isn’t. But I am particularly anxious to have some of the advice in this book followed. And I greatly fear that if I advised more than a half hour most readers would serenely neglect my advice altogether. After you have been able for a month to devote at least one-half hour a day to thinking, you may then, if you choose, extend the time. But if you attempt to do too much at once, you may find it so inconvenient, if not impracticable, that you may give up attempting altogether. Throughout the book I have constantly kept in mind that I wish my advice followed. I have therefore laid down rules which may reasonably be adhered to by an average human, rules which do not require a hardened asceticism to apply, and rules which have occasionally been followed by the author himself. In this last respect, I flatter myself, the present differs from most books of advice. Above all I urge the reader to avoid falling into that habit so prevalent and at the same time so detrimental to character:—acquiescing in advice and not following it. You should view critically every sentence in this book. Wherever you find any advice which you think needless, or which requires unnecessary sacrifice to put into practice, or is wrong, you should so mark it. And you should think out for yourself what would be the best practice to follow. But when you agree with any advice you see here, you should make it your business to follow it. The fact that part of the advice may be wrong is no reason why you should not follow the part that is right.