I'm (involuntarily) great at remembering passwords when I'm at my desk at home, or a PIN when paying for petrol, but at other times in the "wrong" context, I'm totally blank. I read something a while back about methods for subconscious recollection based on an individuals location / state of mind context.
Just now, I forcefully remembered a password by picturing myself at my desk at home. But now maybe I've re-contextualized the memory and I'll struggle to recall it when I actually need it.