Communicate and listen- Recognize how you are feeling and communicate this to your partner often. Listen to and respect how your partner is feeling.
Discuss and plan activities that you will both enjoy. Studies show couples that spend time together participating in activities they both love are more likely to build stronger, longer lasting relationships.
A good idea is to compromise and do what the other one wants one day, and what you want the next (without whining and complaining). Consider it an enriching experience, possibly discovering new things you may not have experienced if you were alone.
Know yourself- If you know you'll be completely unhappy without a long morning shower and a place to plug in your hair dryer, a camping trip to the middle of the desert would turn out disastrous. Not only will you be miserable, so will your partner, who may resent you for ruining the vacation.
If you are prone to mood swings, eating foods in their natural state is ideal. You may want to limit caffeine and alcohol consumption as well to avoid getting headaches and feeling depressed and/or restless.
Take care of each other- Make sure that you and your partner are eating healthy meals and drinking enough water. Good choices include fruits, vegetables, whole grains, and protein sources. Water intake should be a minimum of 8 cups per day, as dehydration is a major factor that affects mood swings.
If one of you becomes ill, try to stay positive and understanding. Think of creative things you can do together. Build a pillow fort in the hotel room, or try some new massage techniques. Your experience is what you make of it.
Give each other space- Don't expect to be joined at the hip the entire time. You are individuals, and you won't always feel like doing the same things as your partner. Spending quality alone time, or time with other people will make the times you spend with your partner more meaningful. Honor your time together as well as apart.
Plan ‘dates' with your loved one and keep them. Knowing that your beloved will be back, say, around dusk, to escort/be escorted by you on a pre-planned evening is an effective counter for that left-behind feeling.
Also, make an effort to meet new people when traveling with your partner. Just because you are traveling together doesn't mean you are closed off to others around you. Meeting new and interesting people can enrich and strengthen your experience.
Spend quality time together- When you are together, have fun! Think positively and smile. It's up to you to keep your mood happy and relaxed. Think sexy thoughts and express them to your partner (without expectations). Be romantic and attentive.
Have a sense of humor and find joy in every situation. For example, if you were stuck in an elevator, you could either get angry and frustrated, letting the claustrophobic feeling cave in on you, or you could pin your partner against the wall and have a sexual experience that others only fantasize about.
If you can make it through a long trip and still love each other more than ever, then you are a very good match and you have excellent potential for a long-lasting relationship. If you just can't seem to get along and have an unhappy time, perhaps this is a sign that you need to swim with a different fish.