The Mishna discusses a case of someone who is half a slave and half a free man (i.e. He was owned by two partners and one partner freed his half) Beis Hillel initially said he should split his time, work one day for himself and one day for his master. Beis Shammai countered that works well for his master but what about him, he cant marry a female slave because of his free half and he cant marry a Jew because of his slave half. To let him not get married is also not an option because the world was created for the sake of procreation. Rather, for Tikun ha'Olam, we force his master to free him, and the half-slave writes a document obligating himself to pay half his value to his master. Beis Hillel retracted, and agreed to Beis Shammai.
We can learn an important lesson for ourselves from the case of a half-free and half-slave person. We are similar to the half-slave half-free person, we are composed of two parts, a Guf (body) and a Neshama (soul). We are constantly dividing our time between these two entities. We should think every moment of the day am I working for myself or for my Master in Heaven.