I feel somewhat the same way, the exam system is based (up until GCSE at least) on your ability to remember facts and repeat them back, this is not a test of intelligence but (what one of my teachers referred to as) the "trained monkey" approach.
The sytem is the best it can be for now, in adult life you can take courses you previously failed or do something different failing is by no means the end.
Regarding illness, I had cancer at age 9 which impacted heavily on my schoolwork, I still passed with 10 GCSEs. I failed my A Levels, did different ones at a different college went to uni, graduated with BA Hons Media Studies and English Literature in May 2008. Couldn't find work and remained unemployed up until now (I now do voluntary work for a company called BTCV).
Education is important but it is not the only thing, most jobs i apply for only care about he number of GCSEs not the actual grades.
In short; school good exams bad, but live with it, bad results are not the end of the world, there are plenty of opportunities to redo or add to your current grades.
If all else fails watch "Everyone is free to wear Sunscreen".