Means you never want to say: "I wish I had traveled, or I wish I had called that person" Time went by, while you did not act.

It means when you look back, you did not do all you wanted, sure. It also means that life seems short. The years feel as though they have not been long for you.

"Time" here is personified. It is like a person whom you do not know walks by you. Do you care? Nope. So it means you have fritter time away.

It means that you are wasting opportunities while time continues to progress.