The land we live on is only equivalent to 30% of the earth's area. It is so small that we don't know who we will meet in the next second. However, the China we live in has 1370536875 people. It is so big that we don't know who will disappear from our lives in the next second.
And in this big and small world, there will always be one person who will leave a trace, deep or shallow, deep in your heart. That is the trace of time, called youth.