Maintain your rest routines. Go to sleep and wake up at about the same times you normally do. Even consider getting up a few minutes earlier than usual to do a few light exercises in your room.
Bring your favorite tea bags or coffee and filters with you. Avoid alcoholic beverages, as they'll ultimately make you feel tired and listless.
Know your needs and limits regarding food. If you've been allergic to peanut butter, dairy, wheat gluten or shellfish, this won't change when you're in another city, state or country. Keep sight of who you are and what is good for you, as you enjoy food experiences in new places.
Bring quick snacks that you know will work for you. Eating roadside fast-food sandwiches, if that's not what you're used to, might not be the best choice for your system. Almonds and dried fruit are a healthful food for road travel. So is good-quality salmon and beef jerky.
Keep up with routine exercise. While you're traveling, you may not be able to exercise as much as usual. That's perfectly OK. Just get out and walk around. Do some stretches and pushups. If you're in a hotel with a gym or pool, enjoy the facilities a little each day.