The essence of service to mankind is to give happiness to others at the cost of your own happiness.
Selfless and real service
That is real service where there is no thought of self at all. Selfless service may not only bring one to the mystical mountain, the summit of which is Self-realisation, but may enable one to ascend a large part of it , or may not only bring one into contact with a Perfect Master but may drive one to surrender to Him.
Selfless service and love are twin divine qualities. Only the one who loves can serve. Serve your beloved God-Man and you are serving your own Self in every other self. This service which the Master exacts is for your own spiritual benefit. However, your service must be spontaneous, willing, wholehearted, unconditional and not expecting any reward.
The best service
The best service is that which makes people start loving me, because in loving me, freedom comes — everlasting freedom! Service to humanity is an important instrument with which my love can be vastly spread."
Highest type of service
Of different type of service, the service which is concerned with spiritual understanding is the highest, because spiritual understanding includes the right perspective to all human problems, and promotes a solution of them all
Absolutely selfless service
Absolutely selfless service is possible only by Perfect Master; but spiritually imperfect, through sincere karma yogis must do their level best to be selfless as they can. He who, driven by love, thinks as little as possible of his own self, and regards all as forms of the oneself and serves others, regardless of caste, creed and colour, is a karma yogi through he may not be aspiring for Self-realisation