‘Slave’ in this context refers to a disciple.

    A disciple should always consider himself to be the servitor and serve his spiritual master (Guru) in the best possible way. Just as a slave does his master’s household duties according to his master’s wish, the feeling should be that ‘in serving Him lies our happiness and spiritual progress’.

    ‘We are worthless slaves; we have done only what we ought to have done’ is an attitude which is important as no matter what one does in the service of the Guru principle, one could never have done enough.

    Nothing that one does can repay the debt unto the Guru who is the only one who will liberate a seeker from the cycle of birth and death just as one cannot repay one’s parents for what they have done. That is why we should never expect to be thanked or appreciated by the Guru, instead should practice Spirituality without expectation (nishkam sadhana) and be grateful that the Guru is giving us the opportunity to do it.