How does work become a sadhana?

It is only when work and action are done in that way, without insistence on one’s personal ideas and personal feelings but only for the Divine’s sake without thought of self that work becomes fully a sadhana and the internal and the external nature can arrive at a harmony. It makes it more possible for the inner being to take up and enlighten the outer action and grow conscious of the Mother’s force behind it guiding it in its works.

Ref: The Mother with Letters on The Mother