If you always try to serve others, you can never make offenses.
Enthusiasm and eagerness in service is the difference between a hollow ritual and a genuine act of devotion.
Service should arise as a by-product of inspiration as it is a devotional exchange between the Lord, Supersoul and jiva.
Every service has a heart, and that heart is Krishna Himself. So when you put your heart into that service, then you will enter the heart of Krishna.
A karmi (non-devotee) who is eager to climb the ladder of success is very enthusiastic to please his boss. Same principle applies in devotional service. Enthusiasm to serve is impossible without eagerness to please.
Service is a privilege which is extended to a conditioned soul by the mercy of Guru.