My vote for “worst chapter break” in the English Bible tradition is the artificial and contrived separation of Matthew chapters 11 and 12.  It is always good to remember that the verse and chapter divisions are not original or inspired as we read the Scriptures!  Below is the text of Matthew 11:25-30 in the first paragraph, followed by Matthew 12:1-9 in the second paragraph.  The words in bold clearly function as the start of the new pericope in Matthew 12, not as the conclusion to the discussion in Matthew 11 (for instance, note the profound connections beween “rest” and “Sabbath” throughout the Old Testament).
Seen in this light, this famous quaint saying of Jesus becomes less a disconnected, abstract truism, and more the concrete fulfillment of a much larger, ancient reality in God’s universe.  Namely, we learn that it is in Jesus that we at last find the rest that the world was designed for (Genesis 1-2), but which was subsequently forfeited (Genesis 3) and never again truly regained afterwards by either Moses or Joshua (Hebrews 3-4, Psalm 95) because of sin:

“At that time Jesus declared, “I thank you, Father, Lord of heaven and earth, that you have hidden these things from the wise and understanding and revealed them to little children; yes, Father, for such was your gracious will.  All things have been handed over to me by my Father, and no one knows the Son except the Father, and no one knows the Father except the Son and anyone to whom the Son chooses to reveal him.  Come to me, all who labor and are heavy laden, and I will give you rest.  Take my yoke upon you, and learn from me, for I am gentle and lowly in heart, and you will find rest for your souls.  For my yoke is easy, and my burden is light.

At that time Jesus went through the grainfields on the Sabbath. His disciples were hungry, and they began to pluck heads of grain and to eat.  But when the Pharisees saw it, they said to him, “Look, your disciples are doing what is not lawful to do on the Sabbath.”  He said to them, “Have you not read what David did when he was hungry, and those who were with him: how he entered the house of God and ate the bread of the Presence, which it was not lawful for him to eat nor for those who were with him, but only for the priests?  Or have you not read in the Law how on the Sabbath the priests in the temple profane the Sabbath and are guiltless?  I tell you, something greater than the temple is here.  And if you had known what this means, ‘I desire mercy, and not sacrifice,’ you would not have condemned the guiltless.  For the Son of Man is lord of the Sabbath.”  He went on from there and entered their synagogue.  And a man was there with a withered hand. And they asked him, “Is it lawful to heal on the Sabbath?”—so that they might accuse him.  He said to them, “Which one of you who has a sheep, if it falls into a pit on the Sabbath, will not take hold of it and lift it out?  Of how much more value is a man than a sheep! So it is lawful to do good on the Sabbath.”  Then he said to the man, “Stretch out your hand.” And the man stretched it out, and it was restored, healthy like the other.  But the Pharisees went out and conspired against him, how to destroy him.”  (Matthew 11:25-12:9)

On a related note, this Tim Keller sermon on “Work and Rest” is the single best resource I’ve come across on what it looks like to rest by faith from our working in the kingdom of God.  And here is a biblical-theological essay that traces the theme of Sabbath throughout the Bible that I have found especially insightful.  Maybe taking a few minutes to ponder such matters might even turn out to be a bit relevant for anxious, workaholic Harvard students?