Self esteem is a good one - I could certainly use more of that.
But actually, my one wish is to be completely and totally Healthy.\
I mean inside and out - no allergies, glasses, cavities, etc. etc. How cool would that be?
I would change my idealism. Or lack of, as the case may be.
There are things about life I wish I was dead wrong about and could believe otherwise in. But experience is a cruel teacher. Ignorance may be bliss, but I wouldn't want to sacrifice intelligence to achieve happiness, so I would rather eliminate all the experiences that caused my present opinions.