Kongtrul Rinpoche suggested we pray to the guru, buddhas, and bodhisattvas and ask them to grant their blessings, “So I may give birth to the heart of sadness.” But what is a “heart of sadness”? Imagine one night you have a dream. Although it is a good dream, deep down you know that eventually you will have to wake up and it will be over. In life, too, sooner or later, whatever the state of our relationships, or our health, our jobs and every aspect of our lives, everything, absolutely everything, will change. And the little bell ringing in the back of your head to remind you of this inevitability is what is called the “heart of sadness.” Life, you realise, is a race against time, and you should never put off dharma practice until next year, next month, or tomorrow, because the future may never happen.
From Not for Happiness: A Guide to the So-Called Preliminary Practices by Dzongsar Jamyang Khyentse, pages 6–7.