I would think for a man that has played football all his life, retiring would be a very sad decision to have to finally make. In my opinion, retiring for any man from any profession would be a hard transition. We all think it is the end all be all of existence....retirement (woo hoo) LOL.
However, I think a lot of men feel they are defined by what they do for a living. That's what makes them who they are. For a lot of men when that is gone, they might have a sense of not knowing who they are anymore. That huge life change might be hard to move into without some feelings of loss or thinking they are missing out on contributing to society.
I don't know what he is going to do. I am pretty sure that if his ankle surgery was not able to fix all that was needed in order for him to play again, he will be extremely bummed out by "having" to retire instead of retiring when he was really mentally, emotionally and physically ready to hang up the helmet.
Putting football aside, the thought of a man who loves nothing more than doing his job, Brett being forced into retirement would be extremely disheartening.