In the decade or so that I have been traveling around the United States for both vacation and work, I have learned a few things about taking time for myself while still focusing on the tasks at hand.
1. If you are going somewhere new or somewhere that you'd just like to see more of for work, look closely at the dates that you are traveling and see if a return ticket a day later changes the plane fare. Even if you pick up one night of the hotel on your personal card or a day of the rental car, it's much less than footing the bill for the entire trip on your own. Consider using one of those vacation days and go exploring for a day.
2. If you're going on vacation to a place where you may also have work, you may be able to spend a couple extra days on the road and give yourself a bit more of a break from your routine by adding some work meetings. If you want to vacation in New York, see if your company would mind you squeezing in a few of those business trips in during your vacation when you're on a commuter flight rather than taking a cross-country trip. You will save the company money on a bigger plane ticket price, plus depending on the radius of your travels, you could also save yourself footing the bill for a couple of nights of a hotel. You win, and you and your company save money.
3. Even if you can't take extra time off, make sure you take time for you. Recently, on a trip to Austin, the property we stayed at had an on-site spa. The meetings that I was involved in had some flexibility for me to be able to squeeze in a massage. I left feeling rested and relaxed, and I didn't skip a beat with work.
4. Don't work begrudgingly on a vacation. If you told work that you don't mind checking email or taking calls even while you're on vacation, still keep to a business schedule. Tell callers on your voice mail that you will be checking voice and emails at certain times each day, and then stick to your schedule. Keep a smile on your face if things go awry and you do end up working more, but even simply sharing with callers that you are on vacation but still taking calls will usually keep them brief and to the point.
When you get caught up in a routine even the more eventful days can seem like they drag on forever. Sure, there have been vacation days where I have spent more time working than I would have liked, but somewhere in the end, I am certain it will all balance out.