I also think, in regards to beginning school with a health condition, it isn't quite the 'in for a penny, in for a pound' you're imagining it to be. If **** hits the fan you can take a medical LOA. Not ideal, but it's an option. I don't say this to give the idea that you enter school with the intention of taking a LOA, bc you shouldn't, but it's comforting to know the option is there if you absolutely need it.
That said, do your best to avoid ever being in a situation where you need to take time off. Set yourself up for success. Seek out friends, find a good mentor, find a good therapist, exercise regularly and eat a good diet. These are all things that help keep stress under control. If you need help, know when to ask for it and have no reservations about doing so.