We're on vacation, why are we exhausted?

Susan and I are getting ready to leave for a trip to Colorado. We honeymooned there and have gone back for each anniversary. Our work schedules and non-work schedules are crazy and we are trying to get everything done before we leave. As much as we will try to avoid it, it usually means a late, late night packing. Then we're tired when we get to the airport and exhausted by the time we get to our destination. We have to come up with a better system.