The Rule of St. Benedict: Chapter 17
What makes a practice a practice, whether it be athletic, artistic, intellectual, or spiritual, is the repetition of actions with the intent to form an ability or capacity within a individual or community. A habit also involves repetition but is distinct from a practice inasmuch as it lacks explicit intention around the formation it affects.
This is not to say that practices are good and habits are bad. Many practices become habits over time and are able to maintain their formational trajectory along the lines of their original intention. The easier the ability to be formed, the more quickly a practice becomes a habit.
Think of driving a car. I haven't practiced driving since I was 15 (or for a few hours after completing my last defensive driving class). Now I just drive, having had the ability to do so adequately formed in me long ago. The more difficult an ability or capacity to be formed, the longer a practice must remain a practice that maintains the clear intention of its undertaking. Professional athletes must practice for as long as they desire to remain competitive. Once the intention is lost and habit takes over, an athlete competing at the highest level loses the edge needed to remain on that level.
The spiritual formation of a human being on a Benedictine path requires lifelong practice. Our Father Benedict desires to form in us the ability to live in God's tent (RB, Prologue), which is really the capacity to bear God into the world (RB, Prologue). This is no easy skill set that one can learn by rote and convert into habit. It requires daily intention of careful practice.
Our prayers can become habitual and memorized over time. There is nothing wrong with this in the least. It is not the ability to pray fluently in one way or another that our prayers are intended to form in us. We learn to pray so that our prayers become a component part of our Benedictine practice with its grand transformative intention. To consider the prayers themselves to be the intention leads to the legalism, judgment, and pride that is a source of much contention in the Church.