One silver lining to having a chronic disease is that you visit the doctor quite often and have your blood tested quite often. For someone that enjoys running and endurance events like I do, those blood tests can be a great tool when things suddenly and unexpectedly go off the rails during training.
Sidenote, it’s also very helpful to have a doctor that is an athlete/runner herself or is used to working with and interpreting blood tests from dedicated amateur athletes. I’ve found my doctor (a dedicated cross-fitter and ultra-runner) very sympathetic to the mental aspects of training, too. When I tell her my frustrations or need to run, I know she understands.