How do you get bad feelings about your asthma to go away?

Bad feelings... ...Are the result of feeling defeated by asthma. Take proper care of yourself, get the upper hand over the asthma, and the feelings will reflect your mastery.
Depression? If you are feeling bad about being an asthmatic, or bad about your body, getting evaluated for depression is not a bad idea. Severe asthma can be a difficult lifelong struggle and the struggle should not be taken lightly. If it has you down badly enough, get treated.