His day will be no better if we worship Him and no worse if we refuse to. What it will do for us and for our day, that is another thing altogether. It is safe to say that God can get along just fine in His universe without me. It is not safe, smart or sane to say the reverse. Jesus' last point can make the issue quite personal.
Humans tend to respond to the urgent rather than the ultimate.
Most of the frustration and meaninglessness in people's lives does not come from missing their target, but from choosing the wrong one. It is more than simply ironic that they had to get the Lord dead and buried before His day got underway. The Sabbath was made for us, not we for the Sabbath. When we fail to observe the Holy Day, we succeed in missing God's direction for our lives. It is no wonder that neither our aim nor our targets are on course.