relationship happiness

I'm often struck by my 3 year old daughter’s natural ability to be present, in pretty much every moment of her waking life, and believe she offers a crucial lesson in the power of now, both for me personally and for my relationship with my wife:

The more present we are with spouses—in spite of daily stressors, like pressures of parenting; in spite of fears about the future, or concerns about the past—the more fulfilling our relationships.

What is it about staying present—which, not coincidentally, is the holy grail for a slew of spiritual teachings—that’s so important?