This quote first struck me as all gooey and romantic, like the early feelings of falling in love.
Upon further consideration, I recognize that this must be true for any relationship to last. Early on in our child-rearing days, we agreed that we needed to provide a united front to the children, both of us "on the same page" in handling situations. We knew that those incredibly smart little souls could easily use any divide between us to their advantage. There were times when we the parents had lively closed-door discussions between us to get on the same page, but we did it. Our united souls supported us in doing the best we knew how for the kids.
I believe another reason we have lasted together so long is that we are fundamentally in agreement relative to financial matters. That prevents a lot of conflict right there.
Lastly, our souls are agreeable relative to each of us pursuing our hobbies and interests. He loves music and doing U.S. bicycle tours. I love golfing and pampered international travel. We are soul-connected enough to allow each other the freedom to have fun as we choose.