Atmabashoubirdheyatma prasadamadhigachchati. (64)
Prasade sarbadukhanang hanirasyopajayate
Prasannachesyo hasto buddhi paryabatishthate. (65)
When a karmayogi enjoys the material world through senses controlled by his mind he achieves happiness; by conquering that happiness he achieves God- that is his wisdom becomes stable in God. (My translation from Bengali, the originals is in Sanskrit, a language unfortunately almost Latin for me)
As per Geeta when a person gets addicted to the results of his works and his work is controlled by that addiction he is inviting self destruction.
On the other hand when his work is selfless he is blessed with true happiness and wisdom. His wisdom becomes stable in one thing – God.