The commander of the faithful Imam Ali peace be upon him says:
اتَّقُوا باطِلَ الأملِ، فَرُبَّ مُسْتَقْبِلِ يومٍ ليسَ بِمُسْتَدْبِرِهِ، ومَغْبُوطٍ في أوَّلِ لَيلِهِ قامَتْ بَواكِيهِ في آخِرِهِ.
‘Guard yourselves against false expectation, for many a person who begins the day does not live to see its end, and many a one is envied at the beginning of the night while his mourners have assembled by the end of it.’
Source: Ghurar al-Hikam, no. 2572