Hi Hamish,
All the issues and thoughts you're having about your experiences being sick with UC, and now living with an ileostomy are perfectly normal.
I wrote to you last year (I'm Marsh) and it's still posted, so you can reread it if you'd like. I'm 50+ years post-surgery, and the 4 years from disease to surgery still replay in my mind. Sometimes, I mourn for what I consider my lost youth, and other times I'm grateful that it was "only" 4 years. Sometimes, I'm angry that my parents refused consent for the surgery in the first few months, and then other times, I fully understand their wish for me to get well and "be normal". I was out of school for 4 years.....which put me out of step with classmates, and even more so, when I returned to school, and saw all the work I had to make up, if I wanted to finish high school and go on to college. More anger, more regret, more sorrow. But I completed high school, had some college, and then finished up, 12 years later, after getting married and having two children (both of which have IBD). One has Crohn's and the other ulcerative colitis. They've had a somewhat difficult time in the early years, maintaining their health, without surgery, but both are doing well now, one on medication, and the other controlled by diet.... It's a blessing. Now.....I just worry about their very young children. So far, the 2 little Aussie boys (9, 6) are well, and our little 7-year-old Princess (here in the states) is okay as well.
It's good that you're seeing a therapist, mostly for you to accept what is, and make a plan for your future. Many people modify what they choose to do (as a life work) after they've been through traumatic illnesses. You might find your life plan changing, as you make your (more) adult choices. I became a special education teacher (for very young children) as a result of my being hospitalized during my school years.... Accepting what has happened to you might become a lifelong challenge.......good for you, in fact, if it helps you guide your path and decisions towards meaningful work. My Aussie son (Jay) is now 43 and lives in Queensland. If you feel you'd like to have a conversation with him.....I'd be glad to introduce you. He doesn't have an ileostomy, but was there for a college friend who needed to have the surgery. We don't talk about (illness) that often, but as a mother, of course, I worry for him...and his young children. His wife developed MS after the birth of their first child, and although she's doing well now, that shadow always hangs over them.....
I wish you the best of luck and continue what you're doing. See the therapist when you're ready, go back to school, reach out to people on this site, or at ostomy groups, to help you listen and learn, and accept. All these things take time....so give yourself that most special gift.....of time. Marsha