Being flexible.

Here are some specific ways to be flexible on a long hike (coincidentally this would also apply for an ultramarathon or other similar endurance challenge):

Be prepared to change your plans. Don't get too attached to a specific route or schedule. If the weather is bad, or you're not feeling well, be willing to take a break or change your plans.

Be willing to improvise. There will be times when you don't have the gear or supplies you need. In these cases, you'll need to be creative and figure out a way to make do.

Be patient. Things will go wrong on a long hike. It's important to be patient with yourself and others, and to not let setbacks derail your journey.

If you can be flexible, you'll be well on your way to completing your 2000-mile hike.

Here are some other pieces of advice that may be helpful:

Start training early. Give your body plenty of time to get used to carrying a backpack and hiking long distances.

Do your research. Learn as much as you can about the trail you'll be hiking, the weather conditions you can expect, and the gear you'll need.

Get in good physical condition. The better shape you're in, the easier the hike will be.

Hike with a buddy. It's always more fun to hike with someone else, and it can also be helpful in case of an emergency.

Stay positive. There will be tough times, but it's important to stay positive and focused on your goal.

I hope this helps!