I get up at 4 every day and just stay on that schedule regardless of what I have going on. Occasionally I'll sleep in and that looks like getting up at 5:15. Sometimes, I need to get up earlier for hunting or skiing, but getting up at 3:30 when you're used to getting up at 4 is no big deal. Once you get used to getting up and doing work: gym/conditioning/training or whatever, then its just not that big of deal. Its when you suddenly have to change your sleep schedule dramatically that it impacts you. If you're used to getting up at 7 and then have to wake up 3 hours earlier, its going to be difficult.