I think that motivation is very important to ensure success in everything we do, and would not be different in the acquisition of a good pronunciation, because, is not so easy to learn a second languange and when someone is learning it he/she will have some difficulty in pronuncing some words, however, when he/she has a motivation to do it, I am sure, this person will do it better.
In my opinion learners who are outgoing and confident are more capable to expose to he foreign language and native speakers, because some of them are not afraid of speaking, even they make mistakes.