Understanding is nothing but a realization of your love. When you see a road up the mountain, it is the road of wisdom. When you stand on top of the mountain and look down the same road, it is the road of compassion. Characters are forms which form in front of us. What we know is how we understand them. If you just see form, you are in the world of delusion. If you understand form you understand emptiness too. The Sixth Patriarch is not saying we should avoid thoughts. Avoiding thoughts would be concentration, not meditation. Rather, we don’t pay attention to thoughts. They pay attention to you, to make you realize what they are. Zazen is, in a sense, a very pure time, but if when you finish zazen some very important thing is left to do, you try to do it. Usually things which arise in zazen are completed as they arise. Big self comes together with your small self who is practicing, and you don’t need to remember what happened in your zazen.
The Sixth Patriarch uses traditional ideas to express his standpoint.