John Ortberg said this quote

The greatest moment of your life is now. Not because it's pleasant or happy or easy, but because this moment is the only moment you've got. Every past moment is irretrievably gone. It's never coming back. If you live there, you lose your life. And the future is always out there somewhere. You can spend an eternity waiting for tomorrow, or worrying about tomorrow. If you live there, you likewise will lose your life. This moment is God's irreplaceable gift to you.