The relationship between emotional state and physical illness
is very complex. However, certain physical symptoms, such as headache, abdominal pain, indigestion, and dizziness are very strongly influenced by emotional state. So in some ways your friend is right that excessive worrying about a problem can make the problem and the symptoms seem much worse.
However, it is not always simple to stop worrying about problem. First of all, it is helpful to talk with your primary care doctor
. This is because often problems are not as serious as we think they are. For example, indigestion is rarely a major medical problem, and your primary care doctor should be able to help put your mind at rest with some simple education.
If this does not work, then the next step would be to seek out a few sessions with a counselor or a psychologist
. Some of us have a harder time dealing with physical stress than others, and it can be very helpful to be able to sit down and talk with someone about this. A counselor will be able to give you some mental strategies for dealing with these negative feelings of worry and stress that you are having a hard time conquering.