Those fortunate enough to have some genuine experience find that the results do not necessarily stay with them. Over a period of time there is a fading away of the experience if it is not reinforced with practice. This is quite common. Even monks and nuns will lose the energy of a deep experience, but it is much more difficult for lay people to retain it. In Ch’an there is a saying: “To hear the Buddha Dharma is not very difficult. More difficult is it to practice. To practice is not very difficult. More difficult is it to realize the Path. To realize the path is not very difficult. More difficult is it not to fall from the Path.” There is another saying: “When you have gotten the Buddha-mind, go to the woods, live by a stream, and meditate. Thus will you nourish your saintly embryo.” When will this baby be born? You don’t know. But, like an expectant mother, you must nourish the saintly embryo.
To have experienced the Buddha-mind and lost it is a great pity. Even so, to see self-nature is to be forever changed. What is the taste of a mango? If you have never tasted a mango, you can’t imagine it. But having tasted it, you still have a memory of it, however faint. Likewise, someone who has experienced Buddha-mind has been changed forever. If he falls from the Path, he is very aware of it, and in his mind there is always the intention to regain the practice. By comparison, one who has never glimpsed Buddha-mind is confused.
— Getting The Buddha Mind by Master Sheng-Yen (page 16-16)