This question is inspired by the recent gender identity topic.
If you woke up tomorrow and found that during the night you had magically been transformed into a fully functional member of the opposite sex, how would you react?
Everyone still remembers who you were but when you tell them what happened they just shrug and say "it happens" and they accept it (part of the magic). Government departments will change your ID for you becuase "it happens", your bank will change your details etc. so there's no problems with your identity being lost, just how you deal with the physical change.