Work or karma is something that is done with our own energy for our selfish interest. Work simply entangles one in material existence, and the result may be seen in that one has no real taste for the Holy Name of Krsna. Service or seva, that is of another type. Service comes down to us from the higher plane through the agency of a Vaishnava sadhu. Such service disentangles one from material engagement.
Service means surrender and surrender means sacrifice.
When we endeavor to serve, to please a senior Vaishnava by carrying out his instruction, then we may receive his mercy. His mercy will give us all success. By the mercy of the Vaishnava-sadhu one receives the benediction of Krsna. Without the grace of a Vaishnava-sadhu, one cannot make any advancement. Advancement can be measured in terms of the taste for the Holy Name of Krsna that one has acquired.