Today is all there is?

Yesterday I would have not said that today is all there is.  I was in my thoughts, which were running rampant with mostly silly and childish ideas about my work, relationships and more.  Today I can say that this is all there is.  Why?  Gratitude, meditation and just a remembrance of what I know and what I don't know, which is mostly what happens when we have a day like yesterday filled with thoughts about yesterday, tomorrow but not now or today.  Today is the true meaning of eternity.