Great reply, pulled some tips from this.Everyone is different. I could easily hike the approach to hawk and time to spare. Others could likely hike the approach to Gooch Mountain Shelter. Others yet can't make it to Springer.
Here is the thing. It literally does not make what I can do. What a "real," "seasoned" thru hiker would do. It is your hike. You must walk the miles. Here is the great about the AT (and simultaneously not so great thing about the AT which Dogwood kind of pointed out), with a guide, there are endless opportunities to camp. Hike to Black Gap Shelter. Still have time and energy to spare. Keep going. Get to Springer/Springer Mountain Shelter. Still got time and energy to spare? Get guide book and look for next convenient water/campsite/shelter and go. At Strover and it is too early in the day, get trial guide and look at Long Creek Falls campsite. Get there. Still have time/energy? Let's get to Hawk Mountain Shelter. How much time do I have left? Can i make it to cooper gap? Sassafras Mountain looks like my first real climb. Damn, there is no water at Cooper Gap. It is a dry site. Do I want to make camp with no nearby water? Do I want to hike with more water then usual to get through the night? How about justus creek? Can I make that?
Preview your hike the day before. Don't memorize it. Just know generally the convenient water sources, campsites, shelters, and of course views. From there gauge your day
Hike until lunch time. At lunch time, get out your guide. How much time do I have left? How much gas is left in tank? Dry sections? Ample water? Climbs? How far can I realistically go? Look for a campsite just before the goal just in case you can't make it. When you get to your goal reassess?
I have to plan each aspect of my hike because I usually have 1 1/2 to 1 3/4 full days of hiking to do 30-35 miles as a weekend warrior. But you are not me. You are thru hiking for Christ sake? What does it matter? You know you will be there for 6 months right? It doesn't matter.
Know the trail. Know your goals. But most importantly, be flexible.