Where'd the fire go?

We've been together for over 2 years and we live together. But over time it feels like the fire is gone. You know the excitement and passion of a new relationship; the butterflies, your heart racing, you can't keep your hands off each other? We've lost that. Now don't get me wrong, I am totally head over heels in love with this man and have no intention to wander elsewhere to find this "passion" but I am concerned. We're only in our 20's and if we've already lost these feelings and have settled into a routine and comfortability with one another are we destined for a life of mediocrity together?

I would love to hear from anyone who has experienced this with their S/O and how it worked out for you.