You need enemies to bitlife finish this job. Throughout your life, you might meet adversaries at will; if you have any, you can check the relationship tab. If not, go into your relationship page, choose a friend, and click the option to become enemies, thus selecting your own foes. While keeping your health is not perfect science, there are several actions you may do in-game to help. First avoid risky life choices like drugs, alcohol, and unprotected sex. With these, your health might entirely drop.