I have psoriatic arthritis, not RA, but they’re VERY similar (just slightly different in how it develops and the genes involved, I think) and I’ve had it since I was 10, gradually getting worse, so I figured I’d chip in. 
Like a lot of people said - the initial first bit really is often the worst, because generally you’re feeling kind of cruddy to begin with (which is why you went to the doctor and got diagnosed) so then you’re feeling cruddy and miserable AND maybe trying different medications. Fun. The thing is - it really does get better once you’ve found good solutions for YOU. So hang in there. I take methotrexate (which is a relatively old-school drug, there are newer ones) and it makes SO much difference for me. All the day to day soreness goes away, and most of the severe flare ups go away or are reduced a LOT.
(I still get to hear about it if I do something really physically hard on a bad joint, like spending all day hammering things - I have it in my wrists - but with methotrexate it’s not ‘crippled’ it’s more ‘take something mild for pain and no more hammering for a couple of days.’ Not much different than someone else who’d overused a joint, just my joints might decide they were over used a little sooner than in a healthy person.
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Don’t just wait for the medication to help, though - you will need to think about other elements, also, like how you use your time and what you’re eating. (I’m not talking about a major diet change, just paying attention to if anything you’re eating makes you feel worse or better. For me, I noticed that high fructose corn syrup and alcohol are both instant flare ups the next day, so I try to avoid them as much as possible, and if it is something I want to have - like a glass of champagne at a wedding - then I know to plan for being worse than normal the next day.)
And like other people said - try to look at what you’re doing and see if you can spread out the physical demands or get other people to help out. With these types of arthritis, it is good to keep moving, but at the same time, being in pain constantly is TIRING. Even if you ignore the issue of it maybe making you not sleep as well, the inflammatory process is hard on your body. So figure out the most important things (classes, job, horse time, whatever) and then look at everything that’s left and see what you can just stop doing for right now, what you can ask other people to help with, what you can break down and do a little at a time on multiple days instead of all at once, whatever.
Then if you’re having a good day, or once the meds kick in (and some of them do take a fair bit to really get going - methotrexate probably takes around 2-3 months to get to where it’s REALLY making a huge difference when you first start it, because they start you on a low dose and gradually increase it) you can always choose to do more on any given day, or add things back in that you had to stop.
To be honest, when the methotrexate is at about the right dose for me and I’ve been on it for a while so the inflammation from the arthritis has really settled down, I can handle something pretty close to a ‘normal’ life. So you can get there eventually, it’s just a case of getting the right medications and adjusting your life while you’re waiting for the meds to help.
(I probably am a bit conservative in my ‘normal’ life - example being if I was going sight-seeing in London with my friends when I lived in the UK, they’d ordinarily just kind of set off without a plan and see how much they’d cram in; since I knew I might not be up for going and going and going like that, I’d make sure that we were frequently enough somewhere that we could sit for a meal or a drink or just where I could sit but they could look around a little, like a museum or a park, so I could take breaks if I needed them. If I didn’t need it, great. If I did, it wasn’t a huge departure from what we were doing. We could just have lunch early or whatever.
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Finally, as far as exercise - and I include horses in this - allow yourself time to warm up SLOWLY. Sometimes a really cranky joint will settle down and improve with gentle exercise, but if you just go and try to ignore it, it gets worse. (My lower back is particularly bad like this - after a long class sitting it can be Very Grumpy, and if I were to leap on a horse right after for a serious lesson I’d regret it. But if I do some stretching exercises or even just give myself a little bit of time on the horse walking around not doing anything except letting the way the horse moves move my lower back, then it gets looser and I’m ready to go.
) Some days, depending on the joints involved, this might mean a bit of hand-walking your horse, or whatever. Just plan it in, so you don’t feel rushed to get to the ‘good stuff’ - heck, a hand walking session can also be a ground manners session for a horse, you know? So sometimes you can combine things you need to do because of the RA with things that need to happen anyway for some other reason. 