I've been Type 1 diabetic for 10 years. Even though my glucose control is excellent over that period (A1C never >6.5%) I've never been able to shake the latent fear that it's a matter of time before I develop complications like retinopathy. What sucks hard is that it's not _just_ determined by insulin and glucose. Exercise, stress, activity level, protein/fat intake, illness, and more can all cause massive variability in glucose levels and insulin sensitivity. Therefore my most successful blanket strategy for glucose control is keeping as consistent a routine as possible: eating the same foods, doing the same activities - at the same time, always exercising regularly, and avoiding spontaneity.
While I've always had anxiety, it's only become worse over the years given the fear of having issues in both day-to-day blood sugar management and in being diagnosed with long term complications. Living with T1D often feels like a case study in applied stoicism.