I'm a pretty grudgeful, brooding kind of lady. When there's someone particularly poisonous in my life, I think about it at night time before bed, playing through the conversations I wish I'd had. I've trained myself to stop holding onto grudges, but on the rare occassion when I stil hold onto an issue and think it through too often, I find myself in a flare up pretty quickly. As a teen, I'm sure you find yourself in stressful social and education situations all the time! Definitely arm yourself with all the stress coping skills you can, whether it be a fresh attitude, yoga, excercise, whatever works for you, because stress is now your worst enemy.
My big tip is to explain discretely to your future bosses about your condition and it's affect on your body in a positive way that shows you take ownership but expect understanding. My boss knows I may have days where I have longer bathroom needs than usual, but he also knows I will make sure I work the hours I need to get the job on that kind of day. I don't let my condition affect the quality of my work and I expect my employer to give me the job flexibility to cater to my condition as a result.