Because of the nature of time, the universe is in a constant state of becoming something else. Everything is changing all the time. But, because of the Laws of Conservation of Energy and Mass, there is always part of what was before persisting in what is now. For example, a fire burns logs, releasing the kinetic energy as heat, water vapor, carbon dioxide, etc. The heat dissipates because the atmosphere is very large, but it doesn't dissappear, it just gets diluted. The water vapor is released into the atmosphere, and those molecules become moisture in a cloud and turn into rain, continuing in the water cycle. In a metaphorical sense, your past selves have "burned" and "released" what you are now. You may consider your past selves dead, but the molecules that made them continue to exist as your current self, even if those molecules are rearranged or are slightly different (we eat food and excrete waste, so our molecules are regularly being exchanged with other molecules in the environment). Those same molecules were once inside the sun. Before that, those molecules existed at the beginning of the universe. So, in a way, yes we are constantly dying and being transformed, but the stuff that we are made of can never die. We are just constantly changing, along with the universe, because we are part of the universe.