Following is a quote from the founder of Ananda Marga - Shrii Shrii Anandamurti - which illustrates one of the key ideas of Ananda Marga átmamoksárthaḿ jagathitáya ca – “self-realisation and service to humanity.”
"Those who think that they can concern themselves with parávidyá (spiritual knowledge) only, and finally, through its help, arrive at self-knowledge, are mistaken. Because while working exclusively for self-realisation – átmamoksártham – the worms of selfishness will burrow deep into the human mind and finally sap all the sweeter and finer human sensibilities, all the generous expansiveness of the human mind, and fling the person into a quagmire of remorse. So the endeavour to attain spiritual realization exclusively cannot be considered an ideal way of life."
"Again, if someone works exclusively for the welfare of the world – jagathitá ya – one should realize that to render selfless service, an absolutely pure mind is required, with the expansiveness of the vast ocean and the serenity of the blue sky. Otherwise, while promoting the welfare of the world, one may develop a selfish desire in one’s mind in a weak moment, as a result of which one may bring harm to oneself as well as the universe. So those who do not aim at self-realisation cannot promote the welfare of the world either."
That is why Shiva propounded átmamoksárthaḿ jagathitáya ca – “self-realisation and service to humanity.”
(Namah Shiváya Shántáya, pp. 145)