hii!! first of all, let me say i have a mental illness myself and i’m studying psychology! i personally decided to go study theory & research instead of becoming a therapist though, but that’s only because i know myself, and one of my biggest triggers is people feeling bad and not being able to help as much as i want to.but that aside, i think it depends on the kind of mental illness this person has, and how they deal with it, what their triggers are... so i’d say it’s definitely possible, but you have to know yourself and your strengths and weaknesses first. if you know it would only make you feel worse, please don’t put yourself through that, but if you think it might actually help you, or you know you’d really enjoy it, by all means, go for it!!just make sure to put yourself first at all times, even when it’s the hard thing to do. remember that you can’t help others unless you’re okay yourself! it’s going to be harder with a mental illness, but it’s definitely possible! (might even give you an advantage because you’d really understand people’s pain maybe??)