4:27. …How may this purpose be accomplished? This is the vital point; how may we develop the faith, the courage, the feeling, which will result in accomplishment?
28. The reply is, by exercise; mental strength is secured in exactly the same way that physical strength is secured, by exercise. We think something, perhaps with difficulty the first time; we think the same thing again, and it becomes easier this time; we think it again and again; it then becomes a mental habit. We continue to think the same thing; finally it becomes automatic; we can no longer help thinking this thing; we are now positive of what we think; there is no longer any doubt about it. we are sure; we know. Haanel
So, enthusiastic repetition spaced over time. I can do that. This skill represents about a half an hour about 200 times a year over about 6 years; 600 hours.