My brother turned 21 while in Iraq.
I felt kinda bad for him, but my dad works at GEAE, so they sent him an awesome care package for his bday, including pics of my dad standing next to an Apache and some other great stuff.

Then when he returned home, he went on a huge clubbing binge, so I guess he made up for not doing a 21st birthday blowout.
be safe on your bday.
don't be stupid.
Know your limits.