Firstly by knowing that it is easier to bring about a change in yourself (which is in your control) than a change in the circumstances (which are not in your control). For instance, if you know that for every stressful situation, you react with anger, just controlling that anger will help you to see the situation in a different light. Most negative emotions like anger, jealousy cause further damage both to the situation and to yourself.
Secondly meditation and pranayam have a definite impact on our health. Controlling the mind through meditation and controlling your breathing through pranayam is known to correct a range of problems right from heart disease to depression. Thirdly, you must learn to have faith in the higher intelligence. Fourthly, think positive! When you think positively and calmly, the chain reaction that follows may have different and less harmful consequences. Just as you dispose off your body wastes and toxin by bathing, sweating, passing stools etc, you must dispose off your negative emotions by making a conscious effect to block all negativity and think positive. At this stage, a cleansing nutritional program will help as being physically toxic interferes with clarity and thought, intuition and positive thinking.
Whilst problems cannot cease to exist, we have to learn to deal with problems better. . For e.g. if things are not going your way, you may react by getting angry and revengeful, others may react by withdrawing and getting depressed, some of you may remain very cool and collected in the same situation and so on! Therefore the answer lies in the manner in which you deal with the situation, rather than the situation itself. It is your reaction to the situation that has an impact on your health. If you react violently it can have an exceptionally strong influence on your physical health. If you react calmly, the situation may not go away but you will be able to deal with more clarity.