We all sometimes talk about stress, and feeling stressed, usually when we feel we have too much to do and too much on our minds, or other people are making unreasonable demands on us, or we are dealing with situations that we do not have control over.
Stress is not a medical diagnosis, but severe stress that continues for a long time may lead to a diagnosis of depression or anxiety, or more severe mental health problems.
You can reduce the effects of stress by being more conscious of the things that cause it, and learning to handle them better, using relaxation techniques as well as other lifestyle changes.