The philosopher Democritus trained himself by going into solitude and frequenting tombs. Plato's Phaedo, where the death of Socrates is recounted, introduces the idea that the proper practice of philosophy is "about nothing else but dying and being dead".

The Stoics of classical antiquity were particularly prominent in their use of this discipline, and Seneca's letters are full of injunctions to meditate on death. The Stoic Epictetus told his students that when kissing their child, brother, or friend, they should remind themselves that they are mortal, curbing their pleasure, as do "those who stand behind men in their triumphs and remind them that they are mortal". The Stoic Marcus Aurelius invited the reader (himself) to "consider how ephemeral and mean all mortal things are" in his Meditations.

In some accounts of the Roman triumph, a companion or public slave would stand behind or near the triumphant general during the procession and remind him from time to time of his own mortality or prompt him to "look behind". A version of this warning is often rendered into English as "Remember, Caesar, thou art mortal", for example in Fahrenheit 451.
Several passages in the Old Testament urge a remembrance of death. In Psalm 90, Moses prays that God would teach his people "to number our days that we may get a heart of wisdom" (Ps. 90:12). In Ecclesiastes, the Preacher insists that "It is better to go to the house of mourning than to go to the house of feasting, for this is the end of all mankind, and the living will lay it to heart" (Eccl. 7:2). In Isaiah, the lifespan of human beings is compared to the short lifespan of grass: "The grass withers, the flower fades when the breath of the Lord blows on it; surely the people are grass" (Is. 40:7).

The expression memento mori developed with the growth of Christianity, which emphasized Heaven, Hell, Hades and salvation of the soul in the afterlife.
The thought was then utilized in Christianity, whose strong emphasis on divine judgment, heaven, hell, and the salvation of the soul brought death to the forefront of consciousness. In the Christian context, the memento mori acquires a moralizing purpose quite opposed to the nunc est bibendum ("now is the time to drink") theme of classical antiquity. To the Christian, the prospect of death serves to emphasize the emptiness and fleetingness of earthly pleasures, luxuries, and achievements, and thus also as an invitation to focus one's thoughts on the prospect of the afterlife. A biblical injunction often associated with the memento mori in this context is In omnibus operibus tuis memorare novissima tua, et in aeternum non peccabis (the Vulgate's Latin rendering of Ecclesiasticus 7:40, "in all thy works be mindful of thy last end and thou wilt never sin.") This finds …

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The Buddhist practice maraṇasati meditates on death. The word is a Pāli compound of maraṇa 'death' (an Indo-European cognate of Latin mori) and sati 'awareness', so very close to memento mori. It is first used in early Buddhist texts, the suttapiṭaka of the Pāli Canon, with parallels in the āgamas of the "Northern" Schools.
In Japan, the influence of Zen Buddhist contemplation of death on indigenous culture can be gauged by the following quotation from the classic treatise on samurai ethics, Hagakure:

The Way of the Samurai is, morning after morning, the practice of death, considering whether it will be here or be there, imagining the most sightly way of dying, and putting one's mind firmly in death. Although this may be a most difficult thing, if one will do it, it can be done. There is nothing that one should suppose cannot be done.

In the annual appreciation of cherry blossom and fall colors, hanami and momijigari, it was philosophized that things are most splendid at the moment before their fall, and to aim to live and die in a similar fashion.
In Tibetan Buddhism, there is a mind training practice known as Lojong. The initial stages of the classic Lojong begin with 'The Four Thoughts that Turn the Mind', or, more literally, 'Four Contemplations to Cause a Revolution in the Mind'. The second of these four is the contemplation on impermanence and death. In particular, one contemplates that;
• All compounded things are impermanent.
• The human body is a compounded thing.
• Therefore, death of the body is certain.
• The time of death is uncertain and beyond our control.
There are a number of classic verse formulations of these contemplations meant for daily reflection to overcome our strong habitual tendency to live as though we will certainly not die today.
The following is from the Lalitavistara Sūtra, a major work in the classical Sanskrit canon:
A very well-known verse in the Pali, Sanskrit and Tibetan canons states [this is from the Sanskrit version, the Udānavarga]:
Shantideva, in the Bodhisattvacaryāvatāra 'Bodhisattva's Way of Life' reflects at length:
In a practice text written by the 19th-century Tibetan master Dudjom Lingpa for serious meditators, he formulates the second contemplation in this way:

On this occasion when you have such a bounty of opportunities in terms of your body, environment, friends, spiritual mentors…

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• Gerascophobia (fear of aging)
• Gerontophobia (fear of elderly people)
• Carpe diem
• La Calavera Catrina
• Mono no aware
• Nine stages of decay
• Mortality salience
• Sic transit gloria mundi
• Tempus fugit
• Terror management theory
• Ubi sunt
• Vanitas
• YOLO (aphorism)