I think the statement is about how we experience our circumstance. Our experience is not rooted in reality itself but in our percption thereof. Our perception is rooted in our memory and experiences. The problem is that the look at reality through a series of perceptual filters and those filters tend to distort what we see. Think about it, somebody cuts you off in the traffic and you react aggressively, why did you react that way? The statement says that you should concentrate on changing the manner in which you react rather than trying to ban al drivers that cut people off. My daughter was complaining this morning about a girl that annoys her and how she wishes the girl would just shut up. I told her that there will always be people that gets on her nerves but the thing is that they are her nerves and that she needs to learn the mental control to be able to turn off the feeling of annoyance. Many people look for control or happiness outside of themselves instead of inside of themselves.