Restlessness is usually over-thinking. We are thinking too much. We have gone beyond what we should be thinking about. We are just carried away by thinking, thinking, thinking. And we are restless. Think of the word "restless". It means we are not "resting". When the mind is focused on calm then we are resting. When it is staying on a theme in a constructive or organized way, then we are also resting. But the minute we are jumping on thoughts here, there, and everywhere, we not resting any more. We are restless. So they are thoughts going out of control. The minute you are mindful and you are actually in control, then you cannot be restless. They don't go together. They can't exist at the same time. And even if you are restless and you're fidgeting, and all of a sudden you become aware, you immediately stop. The minute you are aware, you immediately stop. Mindfulness helps to stop restlessness, as far as the body and mind goes.
Restlessness and impatience are tied in very closely. Does one come before the other, or does the other one come first? When we are standing waiting for the bathroom, and we see it has been six minutes and still nobody has come out, we are impatient. Aren't we then spinning with our thoughts? Restlessness and impatience are coming at the same time. We are becoming impatient because we are restless, or is it the other way around? It is so close I wouldn't worry about it. But definitely whenever we are impatient, we are also restless.
If you are generally restless, say that during the sitting you're restless and somebody coughs next to you, how often do you think, "They're too noisy"? Which means we can't even be patient with a sound, because we were already in a state of restlessness. So one could be there before the other, but they are so closely related that we don't have to separate them.
I would like to add something related to this, because Buddhism is so intellectual. There are so many books about Buddhism. There are a hundred books just of the Scriptures alone. There are thousands of commentary books written by old people, new people. Buddhism is so entertaining on an intellectual level. A lot of people get hung up with trying to figure out words, meanings and definitions. Although personally I have read many books, and understand many intellectually, I don't want to stay at that level very long. I like to get back to the real practice: what do we have to do? Whether it is restlessness or impatience, our work is still the same work. So what is really more important is what are we going to do now about the problem.