His Holiness the 14th Dalai Lama, who recently won a United States Congressional Gold Medal honoring him as a spokesperson for peace and non-violence, is not only universally respected, but he is also venerated by millions of Buddhists who regard him as the Buddha of Compassion.
Drenched with this loving nature, he teaches, like a mother, that those who wish to grow spiritually must be very careful.  "This mind of ours has the potential for accomplishing all the qualities of Buddhahood," he says.  "But these qualities are temporarily obscured by our mistaken belief in the existence of an 'I' and by self centeredness and negative emotions.  These are the powerful enemies of the positive attitude that we have generated."
Clearly, the living master is warning us that our own thoughts, if not looked after more carefully than a precious garden, may become poisonous enough to choke our spiritual progress.  The risk is that they are subtle and unseen.
Just when we think we have reached a peaceful space, just when we think we have begun to understand how to live in harmony with our fellows, have you noticed how out of nowhere something comes up that throws us right off balance again?  We lose our equanimity, our equipoise. The Dalai Lama wants us to be prepared for these surprise attacks.  He says, "as circumstances arise, all sorts of negative emotions, such as desire or anger, can suddenly spring up."
Happily, on the other hand, he suggests, there are numerous antidotes for these.  The most important thing, though, is to apply carefulness and attentiveness.  We need to be always on our guard, so that if a negative emotion or thought arises, or is about to arise, we are able to use these tools and to employ the antidote immediately, at the very moment that the mind is disturbed."
 The Dalai Lama states, "We should therefore make every effort not to spoil our bodhichitta (the mind set on Enlightenment).  We must devote all our energy to this purpose.  There is no knowing when death may overtake us.  At the moment, we may be in good health, but life can end suddenly.  Let us make the best use of our days, being careful all the time.”