Sayyidina Ibn Umar (RA) narrated: Allah’s Messenger (SAW) held me by a part of my body and said, “Be in this world as though you are a stranger or one cutting through the road and count yourself among the occupiers of the grave.” After this, Ibn Umar said to Mujahid ‘When it is morning, you should not trust yourself to make it to evening, and when it is evening, you should not expect to make it to the morning. Seize opportunity of your good health before you fall ill and of your life before your death. For, you could not say what will be with you tomorrow.
[Ahmed 4764, Bukhari 6416]