Learn stress-reduction skills.
Get physical exercise or be physically active on a regular basis.
Get enough sleep.
Eat a healthy, well-balanced diet.
Avoid alcohol.
Limit or avoid caffeine.
Participate in social situations by reaching out to people with whom you feel comfortable.
If you think you are not able to control then it is better to consult a therapist.
Therapy with a psychologist who specializes in anxiety disorders is the place to start. If it's so bad you aren't functioning, your psychologist will recommend a good psychiatrist for medication, but if you can fix it without meds it's always better. Now, if you want to try to fix it yourself and it's not disabling your life, it's like facing any phobia -- you learn relaxation techniques, try to teach yourself that it's your thinking creating the problem, not the situation, and then go do the things you're too afraid to do comfortably starting with the easiest first and keep doing it until your brain realizes nothing bad is actually going to happen and you stop being afraid. That's what a good psychologist will try to help you do, but you do want one who specializes in anxiety problems because otherwise you can end up with a chat therapist who you will talk to for years. You'll learn a lot about yourself maybe, but you want to fix it more quickly than that and there are techniques around now to try to do that. It won't be easy, so don't get discouraged. Peace.