If you are religious develop a prayer that really helps you get connected to God in your heart. Develop that feeling of being connected so that all you have to do is say the prayer and that feeling of pure love, peace and safety will wash over you instantly. It takes practice but it is possible. If you aren't religious, try meditating using a relaxation tape that helps you create a peaceful feeling. Once you have that feeling instilled in your subconscious you can reach out to it when you need it.
Nightmares can also signify deeply rooted psychological problems.
Individuals who have been abused as children will suppress memories at the time of the abuse only to dream of them years later. When individuals begin dreaming of the trauma of the past, it is usually an indicator that there conscious mind is getting ready to remember it. In cases like these individuals should try to seek counselling to help them get through the trauma. If this isn't possible, they should try reading books on child abuse to give them an insight into their situation. This is also indicative of individuals suffering from other forms of post traumatic stress disorder.