In my view, this is saying that husband and wife should work together for the same goals.
This goes back to the very beginning when God made Eve from Adam's flesh as a helper
Genesis 2:20-24 (NIV)
20 So the man gave names to all the livestock, the birds in the sky and all the wild animals.
But for Adam no suitable helper was found. 21 So the LORD God caused the man to fall into a deep sleep; and while he was sleeping, he took one of the man’s ribs and then closed up the place with flesh. 22 Then the LORD God made a woman from the rib he had taken out of the man, and he brought her to the man.
23 The man said,
“This is now bone of my bones
and flesh of my flesh;
she shall be called ‘woman,’
for she was taken out of man.”
24 That is why a man leaves his father and mother and is united to his wife, and they become one flesh.
God didn't create us to labor alone.
Ecclesiastes 4:9 (NIV)
9 Two are better than one,
because they have a good return for their labor:
So when we get married, we have to merge our goals and work through life together. This doesn't mean that the married couple will always see eye-to-eye. That's the beauty of God's design: we see things in different ways to accomplish the same thing.
But when we disagree on something, we don't go to our friends and complain about the other spouse. A married couple should always having each others' interests in mind. Agree on which path to take together and present a unified front to the world.
The best way I've found to agree on a chosen course is to talk it through, then pray about it with each other. Listen for God's response. Don't dismiss the other's misgivings as trivial, for it could be God's answer to your prayer (even if you don't like the answer).
And yes, I believe if you work together long enough towards the same ends, then yes, your happiness and sadness are linked (though I doubt my wife will be sad if Alabama doesn't do well this year).