Watch your thoughts as you watch the street traffic. People come and go: you register without response.
If your day involves walking on city streets or taking the subway, you already know how to detach. In meditation we cultivate a similar detachment from our own thoughts.
When you sit to meditate, treat your thoughts the way you treat strangers on the subway – with dispassion and detachment. Keep bringing your awareness back to the breath or the mantra or whatever you are using to focus your attention and concentrate your awareness.