It's the same with foreplay and sex. Take care of any unfinished emotional business in your relationship. Discuss any problems or dissatisfactions when you're both relaxed and calm. If you need to, seek help from a professional counselor or sex therapist. These people are trained to give practical and sensitive advice about relationships.
Some people believe that yoga can improve sexual function by stimulating hormone production.
In fact, any type of exercise will make you feel better about yourself and more interested in life in general. De-stress your life. Make yourself sit down and analyze what you can let go of. Quit committees and clubs you don't enjoy, and spend the time you gain with your partner. Practice biofeedback and avoid meals on the run.