Pandavas were walking through the jungle and were thirsty. They stop walking while Bhima says I will bring some water for all of us. While in search of water he reaches to a lake which was under control of Yaksha. When Bhima tries to take water, Yaksha says either you give me the exact answer of my question or leave from this place. You can take water only if you give right answer , if you give wrong answer you will die. So Bhima was having two option only either leave or ready for the question. Yaksha asked the biggest wonder in this world. Bhima couldn’t give answer he dies. One by one 4 pandavas dies. At last Dharmaraj comes to lake and gives the right answer. His answer – Daily people watch other people dying, living beings dying then also everybody expects that their life should be stable. They behave with their ego as if they are going to live here forever. This is the biggest wonder of this world.
A beautiful line I found in one book – While you are living don’t think of death. And while you are dying don’t think of living.