IMHO, when you hear Buddhists or mindfulness people say something like, “Life is like a dream,” one thing they mean is that more than 99.99999% of the stuff going on in our minds are thoughts about the past and the future. (Past happiness and regrets, and future hopes and concerns.) Because the only thing that’s real in the present moment is what’s actually happening in only this moment, anything that’s outside of this moment is in a strict sense no longer real.
Being old enough to know what a record player is, I like to think of mindfulness and “being in this moment” as being like the needle on a record player. Your mindfulness is the needle, and you’re only playing whatever musical notes are under the needle at this instant. What’s already gone by the needle is the past, and what’s coming at the needle is the future.
Along this line of thinking I like Eckhart Tolle’s two quotes, “The present moment is all you ever have” (you know that’s true if you’ve ever lost consciousness, not knowing if you’d ever open your eyes again), and, “The whole essence of Zen consists in walking along the razor’s edge of Now.”
(Note: I wrote about this a few days ago in a short post titled, Go beneath the story ... meditation is the tool for that.)