Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Remember death in your prayer, because when a person remembers death in his prayer, it is possible that he will perform his prayer in a good manner, and pray like the person who thinks he will not get a chance to pray after this occasion. And avoid every such act for which you would have to make an excuse."