I first found a version of this ancient Sanskrit poem in The Singing Life: The Story of a Family in the Shadow of Cancer by Elizabeth Bryan (Vermillion, 2008). While the original Sanskrit poem has not been found, I discovered variant English translations on the Internet, and used these to make my favourite version.
Look Well to This Day
Look well to this day:
For it is life, the very life of life.
In its brief course
Lie all the realities and truths of existence.
The joy of growth,
The glory of action
The splendour of beauty
Are but experiences of time.
For yesterday is but a dream
And tomorrow is only a vision;
And today well-lived, makes
Yesterday a dream of happiness
And every tomorrow a vision of hope.
Look well therefore to this day.
Kalidasa ( an Indian Sanskrit playwright and poet active during the 4th-5th Century AD. His work was based on Hindu philosophy.)