It lies in the understanding of just what our purpose is in reality, a purpose which can only be understood when we understand just what reality is. Science has shown time and again that nothing we have seen in nature exists in the comfort of perpetual equilibrium. Change comes to all things. All things eventually must either grow or wither away. Sunny days give way to cloudy days give way to sunny days.
Children come and children go.
Glaciers come and go. Mountains rise and erode away. The sun shines but eventually will burn out. The universe expands and will either contract once again or expand into insignificance as its density dilutes itself into infinite nonexistence. All things change.