My father in law, a REME staff sergeant, went over to France on about D plus 3 and went right through to Northern Germany in the next 13 months. Until he succumbed to Alzheimers he would talk at length about his war experiences which did not seem to have affected him adversely, even though he witnessed some horrific events.
More surprisingly, when I had a shop, a regular customer was a chap who had been a POW under the Japanese. He must have been unusual but he seemed to have coped extremely well with the experience, and had just made up his mind when he got home to accept his good luck in having survived and get on with life. He was well into his 80s when I knew him, and fit and well. He was happy to talk about life in the camps, and interestingly he attributed his small stature (only around 5'5") to the fact that the Japanese left him alone pretty much alone, as they took a delight in picking on tall men.