I've had this problem from the beginning - my brain has mapped "wa" onto "is". I know it's wrong, but it just happens automatically. If I hear "watashi wa", I can't help but think of it as "I am".
Recently I've tried imagining a comma or a pause after the "wa", and that seems to help.
"watashi wa, metablue desu."
Anyone else have this problem? Any suggestions for fixing it?