There is a classic story on impermanence in The Words of My Perfect Teacher. A practitioner did a retreat in a cave for nine years. At the entrance of the cave, there were some nettles. His robes always got caught by the prickly plants every time he left the cave. As it was kind of a bother, he thought about cutting the nettles. Then the thought of possibly not being able to return to the cave again crossed his mind, he decided to do something more meaningful with his time instead. When going into the cave, his robes got caught as well. The thought of removing the nettles arose again. But considering the possibility that this might be his last time leaving the cave, he decided against it and saved the time for training the mind. He continued like this for nine years until he attained accomplishment in his practice while the nettles remained standing at the entrance. It was his firm conviction that all phenomena are impermanent that made him treasure every moment of his life by not spending it on something meaningless but practicing the Dharma. His accomplishment came as the result of realizing impermanence, not emptiness, of all phenomena.

- Quote from The Right View, "The Four Noble Truths—the Path Out of Samsara"

The Buddha once said, “I do not argue with worldly people, but they argue with me.” It means that the Buddha understands where people’s desire and attachment come from. But when people hear the Buddha speak of impermanence, emptiness and not-self, they refuse to accept and constantly raise objections. Actually, it is no surprise that people object since the Buddha’s viewpoints are something they have never heard of or thought about before and are entirely contrary to their usual way of thinking. So object they must. Still, truth is truth. Worldly people can object all they want at first, but eventually they will have to accept it. By worldly people, I do not mean the atheists or the materialists, but people like us who either have not yet learned Buddhadharma or attained realization of emptiness. It is in fact our very own established ideas that are opposing the new perspective.

- Quote from The Right View, "The Four Noble Truths—the Path Out of Samsara"

We must understand that the six realms of samsara are not invented or arranged by the Creator or any personified god. Nor are they some chance happenings, devoid of causes and conditions. They are in fact the manifestations of cause and effect. And the most important cause among all is clinging to the self.

- Quote from The Right View, "The Four Noble Truths—the Path Out of Samsara"

The opposing view of impermanence is the view of the eternalists, which holds that all phenomena abide forever. The eternalist view is an inborn belief of ours. People tend to regard all appearances as permanent and thus develop either a sense of desire for or dislike of them. However, if one has acquired certain understanding of impermanence, one is unlikely to bear a grudge against others for long because enemies do not stay enemies forever. From a subtler perspective, enemies, like all phenomena, also intrinsically cease and arise every instant. If one were to look for some truly existing enemies, one would not find any in the end. The same goes with desire. People commonly believe that wealth and fame are something dependable and therefore pursue them with all their might. Would they still have been so enthusiastic about their pursuits had they known the impermanent and unreliable nature of all things in the material world?

- Quote from The Right View, "The Four Noble Truths—the Path Out of Samsara"

The Four Noble Truths explain the nature, the origin, the cessation and the path leading to the cessation of suffering. Why are there not three or five truths? It is because all that is known or existent can be assigned to either samsara or nirvana; there is no other kind of existence in between. Samsara has its cause and effect; so does nirvana. Two sets of cause and effect make the Four Noble Truths. To explain nirvana and samsara by way of cause and effect is essentially what the Four Noble Truths are all about.

- Quote from The Right View, "The Four Noble Truths—the Path Out of Samsara"

In Beacon of Certainty, the original face of suffering is said to be pure like the sky above the high plateau in Tibet, just emptiness. The great sage Atisha also said in his commentaries on the Middle Way that the nature of mind is clear and unobstructed like the autumn sky. What is perceived as suffering has long since dissolved into clouds of smoke; there are no traces of it left.

- Quote from Are You Ready For Happiness? Don't Let the Paper Tiger Scare You Off, "How to Face Suffering"

The Noble Truth of Suffering encompasses the non-sentient world of land, rivers, mountains and so forth, as well as the sentient world of all living beings in the six realms. In other words, all sentient beings and what their six consciousnesses (eye, ear, nose, tongue, body and mind) come in contact with are all included in the domain of the Noble Truth of Suffering. Because we are in constant contact with both the sentient and the non-sentient world, suffering manifests around us all the time. We ourselves are also part of it. Even so, people have hardly known correctly the nature of suffering, which in turn leads to much distress. It is therefore so important to understand it well.

- Quote from The Right View, "The Four Noble Truths—the Path Out of Samsara"

Certain religions like to stress the mysterious power of ghosts and spirits. Although Buddhism does not deny their existence, it believes the biggest demon in the world is the deeply embedded tendency to cling to the self. Outer demons can only affect our daily life in small ways, such as causing illnesses or obstacles. They cannot bind us in samsara, not even if the ghosts of the entire universe combine their forces. Only clinging to the self has such power. Yet, we have never realized that this fellow, Self, who abides in our mind at all times and whom we are very fond of, is really a demon.

- Quote from The Right View, "The Four Noble Truths—the Path Out of Samsara"

People look at the same problem differently largely because of the state of their mind. Generally speaking, the mind of ordinary people is more fragile while that of the sages is strong. For instance, when the Buddha was about to enter parinirvana, he was surrounded by many arhats and practitioners. Although everyone knew the Buddha was dying and that they would lose not just a great but extraordinary teacher, all the arhats there were very calm. The exception was Ananda, who, having yet attained realization, was still an ordinary person. He stood crying by the side of the Buddha’s bed and could not contain his sorrow. The arhats were not disrespectful. Because they had already realized emptiness, they could pass beyond suffering.

- Quote from Are You Ready For Happiness? Don't Let the Paper Tiger Scare You Off, "How to Face Suffering"