After leaving Morocco and before settling in Egypt, Maimonides visited Jerusalem and prayed at the site of the Holy Temple. Three days later, on 9 MarCheshvan, he visited Hebron and prayed at the Cave of Machpelah. Maimonides resolved to keep these two days—6 and 9 MarCheshvan—as a personal holiday (Charedim ch. 65 [5744 ed.). It does. Everything you earn is manna from heaven. But you can't eat manna direct from heaven. Rather, that manna has to be converted, step by difficult step, from its heavenly state into an earthly form. It's final, most difficult step, to become a part of this physical world. And for that, you need a normal job in this physical world.