Due to the laws of nature, it is impossible to remain inactive. Therefore, it is necessary to do the right thing. Doing right thing means (1) doing things according to swabhava/nature (2) not doing something against your conscience. An empty mind can become devil’s workshop by doing wrong work. Or, an empty mind can be consumed by random thoughts draining vital energy compromising health. An attitude of doing natural work considering it as your need to do so is Karma-Yoga.
Q. How can I work without the expectation of anything in return? Why should I work in that case? Karmayoga sounds almost impossible.