27yo. Cholecystectomy due to vasculitis. Papillary carcinoma due to hashimoto. Diagnosed w/autoimmune suppressor inactive. Told me avoid stress. True?

Yes, Of course! Stress is harmful to our health. So it is always a good idea to reduce stress as much as you can. But it takes a lot of effort to do so, you can only do that by simplifying your life and your work.
Are you sure. You say you have pappilary carcinoma of thyroid.Did you have a biopsy to confirm the diagnosis.Also you say you have hashimoto disease.Cholecystectomy not related to thyroid condition you should discuss your medical condition with your doctor/endocrinologist as to what exactly you have.Papplary carcinoma is not treated by avoiding stress and needs to be surgically treated followed by radioactive a.