Time
Time is something that can't be re-lived and re-winded. Like anything else in this world, things happen with a beginning and end with an ending. It's inevitable, just like the human race. Life and even the non-living things are not meant to live forever or have the ability to replay a moment in time. Things change for better and for worse while life and time keeps lapsing without a stop. For now, we can just hope time heals everything and it does but sometimes it could mean forever.