For some the ending of something is an occasion for sadness and regret instead of recognizing that it is a natural part of life. After all life is a process not something to be gotten over with.
With a small shift in perception a lot of unnecessary sadness could be eliminated from our lives. Change is a part of life and it usually starts when something ends rather than when something begins.
It is the ending that provides the opportunity for us to change something in our life to give us a different present or future outcome. In a lot of situations something has to be over before something new can begin.