Sutra:
182. kaLaiyAvadhu thanakkennap paNNumadhu.

Meaning:
The obstacle to the service (that is removed by the nama:) is, doing the service thinking it is for that soul's benefit.

Sri PBA Swami's Sarartha Deepikai:
What is the obstacle in performing the service?

It is doing the service for the soul's pleasure. The service should not be performed that way. It should be done for His pleasure. Thinking of one's self as the enjoyer or that the act is for one's enjoyment is the wrong end.