Balling or ballin' (in an older sense) comes from the term Goof Balls, which were amphetamines or uppers and were used as a recreational drug. (Also, as a method to avoid sleep by long haul truckers.) Hence, balling took on the meaning of being high or feeling "up". The term can be found in songs like "Thank You, John" by Willie-T and "Zydeco Ballin'" by Lil' Nathan.
I know that you been balling you're as high as you can be!