How possible is it to earn a degree while in the military?

For context, I'm in my first semester of college as a mechanical engineer, and I've been thinking about join the military- Air Force. I want to enlist full time, and take classes to earn a Bachler's degree in mech e while my time in the Air Force.

From your experience, how hard was it to earn a degree, or why weren't you able to earn a degree? What did your path look like? Does the branch you go affect the difficultness?

I would like to hear your take on this based on experience (I don't want to go reserves... that's lame).