First of all, the question in the title should be, "Are these sentences the same?" The first two sentences are similar but have slightly different connotations. The third sentence is very different. "It's natural to go home after doing what I have to do." This implies that this is normal, unforced behavior. Perhaps because there is nothing else to do after you have done what you need to do. For example: it's natural to be tired after a long day in the office. "It's a matter of course to go home after doing what I have to do." This implies that you have an ingrained habit. For example: in the army, it's a matter of course for soldiers to wash their own dishes after eating. "I take going home for granted after doing what I have to do." This suggests that you take the fact that you have a home to go to after doing what you have to do for granted. For example: I take going home for granted after doing what I have to do, despite the fact that three of my co-workers are now homeless.