This quest for perfection involves endless repetition of unimaginable drills to discover the right niche for each athlete. You must always be thinking about what you are doing, feeling each element, to detect the flaws. At the same time you must be thinking about starts, turns, finishes, pacing, and racing. You must be smart to be a swimmer. Then you must take what you feel in the drills and apply it to the actual sets.
Coaches develop sets that are tailored to match the swimmer and the swimmer's needs.
The sprint freestyler, for example, does not do the same workout as the distance IMer. The breastroker does not do the same workout as the butterflyer, who does not do the same workout as the distance freestyler, and so on. But no matter which group you fit into, sets are devised to be arduous affairs. You must push yourself to your limit, and then push past that, over and over again, in every training session you face. You must always force yourself on, performing whatever your coach tells you to do.