Same - part of it may have been natural shifts in circadian rhythms - in college I'd often be up until 3am during the week, not even particularly busy. Just not tired, so I stayed up. Any class up to and including 10am was an active struggle to get to. Now I am regularly up before 5am to work out and typically start work around 6:30.

People absolutely have natural tendencies one way or the other, but if you want to change you can. Too many people approach it as if they're stuck in one or the other.