I think cardio is one of those things that eventually you just get used to it and it's not as bad, but if you don't do it, starting it sucks terribly...
And I get up at 3 for work, so I'm right there with you, I do a ton of walking and lifting for work so I feel your pain there. It's only a part time job, but the 4 hours we put in are harder than most 8 hour shifts, constant walking, lifting, moving period and you're on your feet the whole time, it sucks, but it takes the place of cardio and I'm getting paid for it so that makes it worthwhile