Avoid any “poor me” type of sentiment and emphasize how you have become stronger, more focused, or whatever positive attribute(s) you want to highlight as a result of living with T1 diabetes.
Keep in mind that the college essay is not a soul-baring exercise – it should be used to give admission officers a reason to want you on campus.
Start with an outline or draft and see how it goes. CC does offer volunteers to review your essay if you like.