The Son of Omar (May Allah be Pleased With Him) used to say:
"At evening do not expect [to live till] morning, and at morning do not expect [to live till] evening. Take from your health for your illness and from your life for your death."

(Bukhari)

Allah says in Surah 18: Ayahs 45-46 what can be translated as:
"And set forth to them parable of the life of this world: like water which We send down from the cloud so the herbage of the earth becomes tangled on account of it, then it becomes dry broken into pieces which the winds scatter; and Allah is the holder of power over all things. Wealth and children are an adornment of the life of this world; and the ever-abiding, the good works, are better with your Lord in reward and better in expectation."