When we practice it's important not to think of what we "know", but rather be open to discover that which we do not yet know.
Practicing a movement one has done before can make the impatient student say to themselves "not this again, I already know how to do that" But this is a very unwise approach to learning the art itself. There is an endless well of knowledge to gain from even the most simplest of martial arts practice.
The benefits of martial arts practice on ones body are too great to list. We already know that a proper and complete form of exercise, like martial arts, will lead to an overall perfect picture of health. Your body will change through consistent practice and effort. At times it will be painful. That one extra push-up, that extra inch in your stretch all make a difference. We accept this. We admit that only through physical discomfort can we initiate movement thus inviting change. So then we must also accept that our attitude and perceptions will be just as painful to change, and that when we are uncomfortable and feel like giving up it is at that moment we are most vulnerable. For if we don't carry through the discomfort and invite change into our way of being then we will remain the same. The same wants fears and desires will be there without resolution. Most are stuck there for too long, or worse never get unstuck. But changing the body or the mind is not impossible, it just takes practice. So invite and then relish the presence of discomfort for that is a clear indication that the opportunity to change is before you. So don't consider shrinking away from it, look it in the eye and scare yourself a little, in some cases a lot. It will take meeting the challenge with an open mind. For example the times we think we already know how to do something.
Martial Arts practice will challenge the way you see yourself, others, the world, etc. If you do not allow your practice to change your way of thinking and of doing things then you will miss out on the true art and greatness that awaits anyone who can submit themselves to the process.
A journey in the Martial Arts can be, for anyone willing, the most enjoyable, frustrating, beneficial, life changing, practical, fulfilling, healthy, spiritual, awakening, enabling experience of their life. Let go of what you know so you can truly discover what this journey is trying to show you.