Sometimes you can intellectually know something, but it is a type of detached knowledge that isn't ingrained within you.

Indeed, We may know and understand many concepts, but they still feel like aliens to us that they can easily escape our hearts while we believe they are there.

Past and future are merely concepts resides in our minds, they have no tangible reality. It is our though process that gives rise to them as if they were real. The only thing you can do about both is thinking. And they are there as long as your mind is wandering from the now. Thanks for sharing your experience. :)