Hey, Chip, sorry for the bad prognosis. However, rheumatoid arthritis does happen in some young people. Perhaps more often than you'd think. Two people who were in grade school with me had it. That was in the mid 70s. Back then, those kids did okay, even with the lack of truely good drugs and treatments we currently enjoy.
Make sure your doctor explains everything to you very thoroughly and do not be too intimidated to ask questions. Find out which dietary, pharmaceutical and theraputic treatments are available, what each one entails, and ask very carefully about pharmaceutical side effects. Being knowledgeable about your condition and its treatments is very helpful to maintaining a comfortable and functional state of health.
Aside from that, good old fashioned mule stubborn refusal to let it get in your way will take you a long, long way.