Nature of service and duty

I could recollect following about the attitude towards duty and service that was beautifully explained by P.P Sri Gurudev:

Every duty and service has to be done with "nirapeksha bhavana" (without expecting anything in return). If there is expectation, then there will be attachment, which leads to bondage, which is again an hindrance to realization and mukti.So don't take undue favours from anyone and reduce attachments.