How could Bruce Willis' character not know if he was ever sick?

Rating: Null/10 (20 July 2005)

Bruce Willis had to ask his wife if she ever remembered him being sick before because he didn't know Even if he had never realized it himself, his parents would have surely brought it up many times. And if not his parents than his teachers or relatives. And he would have realized at some point in his life that he has never had to go to the doctor or hospital for a sickness. This is kind of complicated but, if you have never been sick than you would have no idea what it feels like to be sick so if you tried to imagine if you have ever been sick you wouldn't know what to think of, and you would certainly realize that you have never felt sick.
It just isn't believable at all that someone wouldn't notice something like that.