It's an idiomatic expression, "make up one's mind " which basically means "to decide" or "to make one's decision." In the text above, he is saying that he has decided to look at himself as the person he will be in a few years.
When something "paid off," it means it produced positive results, or it was something worth doing. In the text above, he is saying that he has plenty of experiences that prove his strategy (of looking at himself as the person he will be) is a successful one (i.e. is producing good results).
Hope this helps!