For what it's worth, he didn't write this - at the time he was undergoing therapy and his therapist was basically trying to take over his career. He wrote and had Brian record one or two full albums of material that were never released. This is from the album "Sweet Insanity," which was entirely written by the therapist, as far as I know.
Probably Landy (the therapist) wrote some of the words and Wilson wrote all the music. Landy also credited his girlfriend at the time as one of the songwriters.