Google resources for thru-hiking and backpacking for more detail than I'm giving here, which is long enough! You may already know most of this OP, but others might not, so the main concepts are:

Pack light. Except for high-energy snacks, pack freeze-dried foods and something to heat water in. If you won't be able to build a fire along the way, you'll need a lightweight camp stove and fuel for it. If you'll be able to make a fire, make sure you know how to do it safely.

Have a headlamp and extra batteries.

First aid kit. Be sure you also have KT tape and a knife or scissors in case you sprain an ankle or break a bone.

Have at least one bandana. These are amazingly useful in more ways than I can enumerate here.

You'll want a mylar emergency blanket if your overnights will get cold.

Know the predators where you'll be hiking and plan accordingly, whether it's mosquitoes, mountain lions, or bears. Never hike alone listening to music unless it's a very busy trail. You need to be aware of your surroundings.

Pack water, but also know where the water sources will be along your trail. Get a LifeStraw so you can drink from uncertain sources.

If your trail isn't clearly marked at frequent intervals, mark it in some way as you go. This can be small cairns or branches laid in an X or a triangle. You can even use something lightweight to tie around trees, as long as you retrieve it on your way back. The trail back always looks different from how it did going out.

Ways to contact people in an emergency. Not just a satellite phone, but a mirror, a whistle, and chemical glow sticks. There are two things not often found in nature: repeated sets of three, and perfect circles. With a mirror or whistle, you signal three times, pause, then three times again, etc. At night, if you're in a clear area and have reason to believe there are helicopters looking for you, run a string or shoelace through the loop in the top of a glow stick and start whirling it around like a lasso. These are things I learned in a wilderness survival class taught by a highly experienced mountaineer.

Before heading out, give friends an ETA and also leave a note in your vehicle as to your intended route, and a foil imprint of your shoe so rescuers will know your footprint when they try to track you if you don't return on time. I learned this last one in my survival class, too. I also took a tracking class, and you want your specific footprints to be obvious.

Anything can happen when you're out there solo, especially if it's not a highly populated trail. You need to do everything you can to make it easy for people to find you if you get lost or injured.

But once you've prepared for the worst, you can relax and enjoy the best, so happy trails, OP!