We're looking at your thinking mind, and applying some filters as to what thoughts we'll entertain. Today we add a new one: Is it true?
And for today, we're using a very particular definition of true – is it true for your whole mind? Would your mammal (eg a dog) have a sense of what your thought is about, or is it pure imagination (eg past and future), and therefore only available to the monkey?
The analogy we used is watching a movie and getting so engrossed that you're feeling happy/angry/sad, and have lost all sense of sitting in your chair watching something that isn't true. We want you to keep some sense of what is actually happening – the truth that your deeper (emotional, physiological, etc.) minds can never lose. Don't get so lost in the movie of your life that you end up living your whole life there!
When you find yourself thinking about things that are purely imaginary and have no basis in reality/presence, leave them. And when you find yourself thinking about things that are connected to the present moment (that your dog would also be aware of) engage with those thoughts (if they're necessary!) with a degree of present awareness.