Tibetan Buddhist meditation on death.
Purpose: to overcome the attachment to worldly activities
Preparation: relax, pacify your mind
Contemplation: We think 'I shall definitely die. There is no way to prevent my body from finally decaying. Day by day, moment by moment, my life is slipping away. I have no idea when I shall die. The time of death is completely uncertain. Many young people die before their parents, some die the moment they are born - there is no certainty in this world. Furthermore, there are so many causes of untimely death. The lives of many strong and healthy people are destroyed by accidents. There is no guarantee that I shall not die today.'
Meditation: After contemplating these points we mentally repeat over and over again: 'I may die today, I may die today', and contentrate on the feeling it evokes. Eventually we shall come to conclusion 'Since I shall soon have to depart from this world, there is no sense in my becoming attached to worldly enjoyments. Instead, I will devote my whole life to practice of Dharma.' We then meditate on this conclusion for as long as we can.
Meditation break: During the meditation break we should try to practice Dharma without laziness. Realizing that worldly pleasures are deceptive and that they distract us from using our life in a meaningful way, we should abandon attachment to them. In this way we can eliminate the main obstacle to pure Dharma practice.
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Well, that's the 'official' thing.
You can modify it so as to concentrate on the first part - the feeling evoked by realisation that death can come at any moment and take anyone you know - including yourself.
Or if you find any other part useful - use it.