Human is the strangest species in the world, because we are good at thinking. When we begin to think, we always think the problems that we don't know how to figure out. In that case, a new thing creates,it is stress! When we are under stress, we begin to think how to reduce sress. So, we are very strange. Maybe other animals always laugh at us! They might think that if having enough food and sleep enough, that's enough! So,I even think that other species are better than human. They never do a thing that eventually has a bad effect on thenselves, but human do it every day! we always claims that we are the strongest species on the world, but we were almost defeated by Covid-19. We relax ourselves today, but we make us under stress tomorrow. The loop continues until the death! why we are so sensitive about everything around us? The people who are old enough also feel upset evert day. The worse thing is that we clearly know that relaxtion gives us good feeling, but it seems like that the only task for us is to make oueselves unhappy every day!