A few ideas that might help... (shh... top secret)
1) Pad your project timeline so you'll have time to take a vacation.
2) Pretend you're struggling so you can look like a hero when you complete on time.
3) Be brilliant... that way, you won't actually have to worry about missing your deadlines.
Well, I'd take them no matter what. I don't agree with businesses giving employees a ton of work and expecting it all to be done without regard even for rightful vacation time. It's nonsense.