Find out what the central sentence of this passage is and say what it means.

Flowers bloom when they fall, and gather when they disperse. Without that helplessness, how can we cherish it? We always spare no effort to pursue that eternal, we always try our best to keep that result, but we don't know whether there are old or young. How can there be constant love in this world? But I don't know, if I ever had beauty, I don't need to force any results. There are many things in this world that are not.