That was a bit of hyperbole-- but we do have to be prepared to alter our plans. This can be frustrating to me because I have a peculiar fondness for finishing completely and at the time I previously decided we should be done. (It's that checking-the-box satisfaction, you know.) I am reading a book of speeches that C.S. Lewis gave during his lifetime, and found one that is apt for the beginning of a school year. This quote may help me keep my head in the right place this year:
A more Christian attitude, which can be attained at any age, is that of leaving futurity in God's hands. We may as well, for God will certainly retain it whether we leave it to Him or not. Never, in peace or war, commit your virtue or happiness to the future. Happy work is best done by the man who takes his long-term plans somewhat lightly and works from moment to moment, "as to the Lord." It is only our daily bread that we are encouraged to ask for. The present is the only time in which any duty can be done or any grace received. --from "Learning in Wartime"