“A note to the forgetful: be thankful you don’t remember everything. It means your brain is working properly.”
Researchers have used a simple test which suggests that whenever you’re engaged in the process of remembering, the brain adapts and ‘re-weights’ competing memoties – suppressing those of lesser importance and thus lessening confusion.
Real life examples of this in action: changing to new passwords, PIN numbers, phone numbers etc. confuses me, but eventually I usually manage to remember the relevant ones (unless I haven’t used the current one for a long time – and then instead I tend to be able to remember one I should have forgotten… which can be a problem!).