I think our inherent 'Britishness' makes it difficult for us to do this, in a way that Americans don't feel because they are more comfortable with communication, self-awareness and honesty than are we.
When I look in the mirror, I honestly feel as though the person I see is not me - not in the sense that I dislike my image and wish it was different (I do!) - so I don't think this would work for me.
That said, I am perfectly content with who I am and who I am not, so I don;t really need the affiration.