Many Americans admit they have a tough time taking a vacation.  More than 60-percent of the respondents in the Best Western Vacation Citation survey say it was hard for them to take time off work over the past 12 months, and many expect that they won't be using up all of the days they're entitled to take this year.  More than half add work concerns prevent them from really unwinding while they're away.  Fifty-five-percent simply cannot let a full five days go by without checking their work e-mail or voicemail, while 45-percent say five days is the longest they can go without checking in.  But 64-percent also admit their job is why they need a vacation in the first place.  But work demands aren't the biggest vacation obstacle.  A third won't take all their vacation time because they're worried that they'll spend too much money, while 16-percent say "too much work" will keep them from taking all of their allotted time off.