Bring it back by the scruff of the neck.Ere you have reached the station you will have brought it back about forty times.Do not despair.Continue.
Keep it up.You will succeed.You cannot by any chance fail if you persevere.It is idle to pretend that your mind is incapable of concentration.
Do you not remember that morning when you received a disquieting letter which demanded a very carefully-worded answer?How you kept your mind steadily on the subject of the answer,without a second's intermission,until you reached your office;whereupon you instantly sat down and wrote the answer?That was a case in which *you*were roused by circumstances to such a degree of vitality that you were able to dominate your mind like a tyrant.
You would have no trifling.You insisted that its work should be done,and its work was done.
By the regular practice of concentration (as to which there is no secret--save the secret of perseverance)you can tyrannise over your mind (which is not the highest part of *you*)every hour of the day,and in no matter what place.The exercise is a very convenient one.If you got into your morning train with a pair of dumb-bells for your muscles or an encyclopaedia in ten volumes for your learning,you would probably excite remark.But as you walk in the street,or sit in the corner of the compartment behind a pipe,or "strap-hang"on the Subterranean,who is to know that you are engaged in the most important of daily acts?What asinine boor can laugh at you?