One of my former math teacher's favorite saying was, "you must know it like you know your name..." It's funny the things that you never forget and it's also funny how something like a little saying can be applied to amost anything including the martial arts.
Whether what you're training is practical or not, if you train it enough, you'll get very good at it... I often use this phrase with my students in order to get my point across to them about the importance of training away from class.
But lets take this saying a little further and say, "You must know the movements like you know your name and then adapt accordingly... " Okay that last part I borrowed from a famous Silat teacher who would often say, "you must accept, adapt, and act". Never the less it's very true because no matter how proficient you become at techniques or drills, unless you can adapt to your opponents response, what you're doing is just not very practical.
The other day during training I was demonstrating a combination of strikes and using one of my senior students as a demonstrator. After a while my student would respond to my combination and counter with his own techniques. Each time he countered I recountered in a different way according to what he did. An onlooking student with a puzzled look said, "how can you dissolve these counter attacks so quickly and fluidly?" I told him, "You must know the movements like you know your name and adapt accordingly".