I think the main reason for success is consistency. It's much easier to be consistent on a daily basis rather then working really hard a few days to "gain momentum". Think about it this way. Imagine, instead of brushing your teeth 2 times a day, you brushed them one time a week for 3 hours. That would suck right? Well, that's exactly like success. It's much easier to just do what you are supposed to do for the day.