Oh, well then a more correct phrase would have been "I did and didn't want to" instead of "I can and didn't want to."

JRWakeboard: 'Cause I just don't see how that's possible.
WetWired: I can and didn't want to.

Since he said "I just don't see how blah blah blah" you should have said "I did and didn't want to." If he had said "I just can't see how that's possible" then "I can and didn't want to" would have been correct.

English lesson for the day.