I suppose it's true. All protagonists want something, and if the author has done their job, that protagonist yearns for that thing (or person) more than anything they've ever wanted.
In Robert Olen Butler's From Where You Dream, he talks a lot about yearning. Not only does he devote a chapter to it, but that it is the basic building block he uses for all good fiction.
"It's the dynamics of desire that is at the heart of narrative and plot," he writes. He's also quick to point out that in genre fiction authors never forget this fact, and yet in literary fiction, it's often pushed aside.
What does yearning looking like? First, the author must know exactly what it is that the protagonist desires, and must show the reader this desire early in the text, and they must have sufficient motivation to fulfill that desire. Along the way, as they encounter conflict, they must overcome the obstacles to obtain what it is that they yearn for most of all.
Here are books from my own shelves where you can extract the protagonist's desire from the title:
Look Homeward Angel, Thomas Wolfe home
I'll Fly Away, Wally Lamb freedom
Clay's Quilt, Silas House family
The Age of Miracles, Karen Thompson Walker rescue
The Language of Flowers, Vanessa Diffenbaugh understanding
Middlesex, Jeffery Euginides identity
Grace (Eventually), Anne Lamott God
So for this Valentine's Day, think about what your characters love, and make sure that their journey to obtain it brings the reader along for the ride!