You can accomplish this result by tensing the will and by strengthening the active function of your mind and thus enabling it to “step in” and simply ‘command’ the passive function to drop the old thought-habit and take up the new one.
This is a magnificent feat and in it only the strongest succeed. You can obtain good results by combining this with auto-suggestion. Silently concentrate upon your passive mind and impress upon it your order. Say to it earnestly, confidently, and masterfully: ‘You, my mind, I want you to be fearless, pure, loving and unselfish!’ Picture to yourself in imagination as if you were already these, and again command and impress your will upon your mind.
Do so silently and constantly and never neglect a chance of expressing these qualities in action because, at first your mind will rebel, but if ‘you’ keep up your efforts determinately and firmly and avail yourself of all opportunities to ‘act out’ your will, your mind will end up by accepting your suggestion and manifesting same naturally as a habit. Some of you will actually go out of your way to ‘act out’ a thought when you realise that the easiest and surest way to check and utterly ‘destroy’ a thought-habit is to refuse deliberately to let it manifest in action and to ‘create’ a new one all you have got to do is to equally deliberately ‘express’ it in action and thus clinch it into permanent strength.
Also you must aim at ‘thoroughness’ and guard against all compromise with your lower nature. Chastity must be perfect chastity and nothing short of that, and so on in all development.