This is especially true of people who have a mild TBI and are observed in a familiar environment. Once their surroundings change, their impairment is much more obvious. I read a horrifying thread on Reddit written by a woman who had just had a baby and was concerned because her husband had moved into an RV in their yard because he "needed space". He was still going to work and otherwise acting normal. It turned out that he had been a semiprofessional boxer in his late teens and early twenties, and the chronic trauma to his brain had given him dementia before he even turned 30. She investigated further and learned that he could only keep working because he kept extensive notes about how to perform all of his daily tasks, and his boss and other coworkers were picking up the slack and not pushing him to start taking on new duties. The wife hadn't noticed because they had such a strict routine until the baby came along. In one post, she said that when he held the baby for the first time after his diagnosis, he started to cry and said, "This is supposed to be the happiest time of my life and I can't even enjoy it."