So then each one of us will give an account of himself to God. (Romans 14:12)
Most of what we do, say and think has little or no lasting value. That is not to say that nothing really matters. It does. Sometimes things that at first might seem inconsequential, have significant good or bad consequences. King Solomon wrote; "Vanity of vanities," says the preacher, "Vanity of vanities! All is vanity." (Ecclesiastes 1: 2,) His point is not that everything is meaningless and insignificant, but that most things in life are transitory, a mere disappearing vapor without permanence.
As you get older, you realize how short life really is. There are no "do overs" or "mulligans". We have but one life to live. All of our days so far are already in the books, literally in God's books; And I saw the dead, the great and the small, standing before the throne, and books were opened; and another book was opened, which is the book of life; and the dead were judged from the things which were written in the books, according to their deeds. (Revelation 20:12)
The Apostle Paul understood the importance of moving forward and focusing on the things that matter; Brethren, I do not regard myself as having laid hold of it yet; but one thing I do; forgetting what lies behind and reaching forward to what lies ahead. I press on toward the goal for the prize of the upward call of God in Christ Jesus. (Philippians 3:13)
Since we can't change the past and realize life is relatively short, we ought to continually prioritize our remaining time and focus more on the things that really matter and that are lasting. What will last forever? God; His Word; His salvation given to us by grace through faith; All people also will last forever, some who have eternal life in Christ and most who are not in Christ who will suffer eternal death without Him. These things will last forever and therefore are things that matter!