What is "sesshin"

A sesshin (接心, or also 摂心/攝心 literally "touching the heart-mind") is a period of intensive meditation ( zazen) in a Zen monastery.

While the daily routine in the monastery requires the monks to meditate several hours a day, during a sesshin they devote themselves almost exclusively to zazen practice. The numerous 30- to 50-minute-long meditation periods are interleaved with short rest breaks, meals, and sometimes short periods of work (Japanese: 作務 samu) all performed with the same mindfulness; nightly sleep is kept to a minimum, at six hours or fewer. During the sesshin period, the meditation practice is occasionally interrupted by the master giving public talks ( teisho) and individual direction in private meetings (which may be called dokusan, daisan, or sanzen) with a Zen Master.

In modern Buddhist practice in Japan and the West, sesshins are often attended by lay students, and are typically one, three, five, or seven days in length. Seven-day sesshins are held several times a year at many Zen centers, especially in commemoration of the Buddha's awakening to full enlightenment (anuttarā-samyak-saṃbodhi). At this Rohatsu sesshin, practitioners seek to relax and quiet the mind to the point of cessation of mental chatter and emotional impulse, samadhi, kensho, or satori.