ماضي يومك فائت وآتيه متهم ووقتك مغتنم فبادر فرصة الإمكان وإياك أن تثق بالزمان
What passed from your day is gone, and whatever time left from the day is uncertain, but your present moment can be seized. So make use of the opportunity and never trust time.
Your power and control is over the present moment, you cannot control the past and you are not sure how long you will live. So make the best use of this moment and never trust time, because you never know what happens next.
This advice is in the context of sins and repentance, the Imam is advising us to make use of our time to repent. But it is equally applicable in other areas of human effort.