Oh, boy, this is the excuse I loathe the most. Throw that, “I’ve got too much work to do,” excuse out the window! Why?
You may be a superstar at work, but your employer can exist without your superstar abilities for 10 days. If they couldn’t, then how did they get by without you before they hired you?
Besides, if you’re so valuable to the point you’d never be able to take time off work, why didn’t you tell them at first hire that they can just forgo letting you accrue vacation days in the first place?
Sounds silly, right? Accruing vacation days are done for a reason. You’re human, not a machine, and humans deserve paid resting periods for hard work. So, go on! Take those two weeks off and treat yourself to some traveling. That is plenty of time to recharge.