You must act without the anticipation of the result.........

Thou hast power only to act not over the result thereof. Act thou therefore without prospect of the result and without succcumbing to inaction.    The translation follows thus

Karmani ave adhikars te

--you have the power to act only

ma phalesu kadachana

--you do not have the power to influence the result

ma karmaphal hetur bhoo

--therefore you must act without the anticipation of the result

ma sangostu akramani

--without succumbing to inaction