OMG I know EXACTLY what you mean. After 15 days on Kauai in April, it was totally surreal coming back to 'real life'. I felt like I was in a fog at work - all I could think about was our vacation, how much I wanted sex every morning again, how much I missed him all day, etc etc etc etc. It took me a good two weeks to finally come back to earth 100%.
It's hard to keep that feeling - well, impossible, really, to feel like you just got home all the time. But you can keep the spark alaive. Just keep acting like teenagers together. The icky gicky pet names for each other than everyone else would think are horrible if they heard. "I love you" "I love you MORE" "No, I love YOU more" etc etc. Cuddle, kiss, hold hands. Send goofy e-cards. Send sexy emails. Flirt. Whenever you're together, just act like you ARE on vacation.
It also helps me to have at least one more future trip planned. We do Grey Cup every year. We also had a Sept camping trip planned before we left. This weekend we're going away for a couple nights. All stuff to look forward to as another romantic time to spend together. Planning little surprises for these trips does wonders too