I know you folks with children crept into your child's room in the middle of the night to gaze at their sleeping face. And you were filled with such overwhelming emotion it near brought you to tears. Or it actually did.
Perhaps you have awoken in the middle of the night and turned to look at your partner, resting there beside you, and reached out to softly touch their face, and there was that heart-filled feeling.
And then there are our pets...something about watching them sleep, all soft and quiet and peaceful.
Maybe that's it - in sleep those we love are at peace. They are safe and under your protection. And you want to want to keep them that way - safe, peaceful, and loved.