The most mentally healthy people I have ever heard of are the Cousteau. Looking at the lives of all of them, including the children, I am amazed at how very amazing is the product of one's life when one has always been sane. The impact is huge on the regular people like us. The impact of their lives' work. 

P.S. Even if reincarnation exists, I am  not so sure I will have earned sanity in my next rebirths. I am a being of small capacity.