I think there are limitations to how much someone can change. The analogy I would use is physical traits, you can loose weight, or you can exercise and increase strength and so on but there are limitations. I am 59 and no matter how hard I train I am not going to be able to run a 4 minute mile but I am sure if I worked at it a little harder I could improve my running skills. Similarly, I think one can, through therapy, meditation or other types of mental fitness activities, can make improvements if they have the sufficient desire to do so, but within limits.