I waited a long time for a friend to return from overseas, where she would spend two weeks here on holiday... and in the blink of an eye, she arrived, her two weeks were up and she is gone again.
They say, time flies when you are having fun. Well, no matter if it's good times or bad times, time will still pass. No matter how bad the situation is, it will pass. There is no need to be too sad or two happy over something because it won't last. It's not sustainable.
One time, a friend told me that she was so overwhelmed with a project she doesn't know what to do or where to turn, I, who could not help her just told her, don't worry, this would soon come to pass...and it surely did!