"One of the best ways to remain appreciative of life and all its pleasures is to dwell continuously on its opposite, death.

"Therefore, a useful exercise is to focus the mind every day, preferably just after waking up, on the possibility of imminent death. Particular focus can be achieved by looking at blown-up images of viruses and bacteria that commonly circulate in the air and thrive in our public spaces.

"A few of these are rapid killers and the random chance that one might encounter one in the day ahead should lend a particular clarity to one's quotidian toil. Not least, these germs have a habit of looking beautiful and haunting when seen under an electron microscope."

Alain de Botton, philosopher