Both, I'd say.
It ruined my life by making me sick, as well as causing anxiety and depression. It's also made me want to rule about 2 years out of my life, because thinking about the bullying and the illness that followed it makes me sad and I don't like talking about it when my friends bring it up out of curiosity.
However, it's also made me stronger. This bullying occurred when I was 12 years old, and at the age of 17 I can thankfully say that the sickness affects me far less than it used to. It's also made me stronger in that I've learnt to live with this, and haven't let illness interfere with my education. I had to miss a lot of time off school, but ensured that it didn't affect my grades and ended up doing better than the girl who bullied me. Result! Most importantly, it's given me the strength to intervene, and if I were to spot someone being bullied in school (or even outside of school), I'd report it to the necessary people and ensure it is dealt with. Call me a snitch, but I'd much rather speak up and resolve bullying than leave an innocent victim suffering in silence merely because their life has been ruined by bullies like mine once was.