Pilates is a mind-body movement.  Control begins with the mind.   Your mind formulates and controls the movement. Most of us know from personal experience that it is often harder to do something slow and controlled vs fast and with momentum.  Every Pilates exercises focuses on complete muscular control of a movement.  Lack of control is a primary cause of injury.  Pilates focuses on control instead of intensity or repetition.  Our exercise culture typically emphasizes the latter and believes in working as hard and as fast as possible.  With practice, control is developed and becomes more natural.  It is an essential component of mastering a skill.   Do not be mistaken, Pilates is not slow all the time!  Once you develop control, you can speed things up.  You can definitely get your heart rate up and break a sweat.  I believe as with any skill, it is important to return once in awhile back to the basics, as a means to learn how to better control and further develop your practice.