Medical crisis on a solo cross-country

I had just taken off from Aurora, Missouri (2H2) heading toward Grove, Oklahoma (KGMJ), flying at an altitude of 4,500 feet. I was a student pilot, and this was my first solo cross-country experience. Everything seemed to be a pretty standard day; the weather was nice. The one big mistake I made I had no way of knowing or preparing for, but it happened all the same.