Your Professor is living a miserable life, I promise. YOU should be your #1 PRIORITY in life and therefore you should reward/treat yourself by traveling to Belize or wherever you wish. It's only a week out of life!
I can't believe people who think like this. I was 'brainwashed' into this sort of thinking for 5 years at the company I worked for. All I did was WORK, work, work, all the time for 5 years in my early, early 20's. Then I realized "What will I have to look back on when I am 50?" So I moved down here

And GLAD I did. Creating lifetime memories, friends, and special moments.
10 years from now will it really matter if you went to Belize and perhaps did not get something else done that week at home/studied less that week, etc... What WILL matter is the memories you made while taking care of your #1 priority...you.