Create a Valid Excuse Policy, which is a list of acceptable reasons you or your partner cannot exercise. A sick child that has to stay home is a valid excuse. You feeling down or tired isn't.

Exercising with a partner is as much about the conversation as the workout, but research conducted by Amanda Rose, an associate professor of psychological sciences at the University of Missouri, found that talking about your frustrations is only helpful in moderation. When we complain about our problems endlessly, it can make us feel worse. If your workout buddy insists on talking about problems, guide your conversation to more positive topics.

According to Dr. Michael Rozen from Cleveland Clinic, a workout partner should be like the GPS navigational system in a car: it guides without judgment. If your workout partner misses a workout or confesses to indulging in a pint of ice cream, don't criticize her.

Leadership development coach, Dr. Judith Rich, states that our biggest fear about honesty is that other people will be hurt by our words or will not like us. Regardless of these worries, avoiding the truth will not do your partner any favors. If he is headed down the path of a sedentary lifestyle or overtraining, offer to help and express your concern in a non-judgmental way (see #3).

Exercise is only one part of the fitness equation. You don't have to skip your long talks in the coffee shop after your walk, but keep it healthy. If you notice that your post-workout meetings are beginning to resemble a full breakfast buffet, it's time to suggest that you both get back on track.

Don't let a partner's cancellation be your excuse for not exercising. The American Academy of Family Physicians lists sticking to a regular time as a key to making exercise a habit. There is no reason you can't stick to the plan even if your partner can't. If you keep your commitment, your partner will likely do the same when an unexpected event forces you to cancel in the future. Your choice to exercise alone can provide motivation for her later.

When it comes to weight loss or fitness achievements, no one will know how hard you worked to achieve it better than your workout partner. Take time to celebrate when you reach your goals, then map out the next milestone you will work toward together.