Hey I'm right there with you...I'm not much older than you but I'll give you what little words of wisdom I have. I'm 25 and was recently diagnosed myself.
I hear "suck it up" on a daily basis from my family. I often battle within myself saying "I'm young I should be able to do these things" too.
Now, I wasn't nearly as active as you have probably been all your life. My parent's theory is if I had listened to them all my life and been more active, that I wouldn't be in this situation. Obviously no matter how active you are, RA can attack and leave you feeling awful about yourself.
I don't get a lot of support from my family. I know they love me deeply and want to do something, but maybe they just don't know what it is...I don't know. But their love for me is strong and is always there!!
But over the past few weeks, I have been doing so much research, that I have found a new strength in myself that I didn't know was there before. You can find a similar strength too. You're an athlete so I'm sure you have a lot of strength already!
This is what I found out in my research. Yes rest is good and getting the right amount is important, but that doesn't mean you can't be active. Just that you may have to re-adjust how active you are. You may have a "new normal" and may have to change how you view you and your limitations. You can still LIVE your life, but I'm sorry to tell you it's probably not going to be what you had in mind for yourself.
You're whole life is in the process of a great change, and from experience, I know I hate change and generally everybody does. As long as you're willing to accept that change and are ready, living with RA can be managed and you can do anything you want to do!
I have found some things you can change in your diet to help with inflammation, krill oil helps a lot and unlike fish oil doesn't have a horrible after taste, range of motion exercises and anything low impact...(running may not be the best thing...). I have tons of links and information saved so I can share anything I have found with you.
Let me know if you want to know something specific and I'll post links here for you!
~Surehope
DON'T GIVE UP HOPE!! Life's not over, it will just have to be a little different from now on.