It's not one of those things you can cognitively learn and say "Okay, that makes sense, I get the concept", and leave it at that (although that's true for all concepts in DBT). You truly have to practice it, and it's the hardest to practice because you can't say "okay, I radically accept this and it's all okay". You have to really mean it. Until then, you're doing something called turning the mind (which is repeatedly turning your mind toward radical accepting).
I've found this incredibly hard to do with my RSD/CRPS. Partially because I thought that radically accepting meant that I had to call my CRPS good. I just don't think that way. I think RSD sucks. But radically accepting my CRPS has actually meant realizingg that my CRPS is what it is.
Screaming at the CRPS will only give me a headache, make me feel lousy emotionally and just make me suffer. I've done it for years. It caused me so much suffering, in so many ways, I can't begin to tell you. Some of those things are things I can't write about here.
Another barrier to radically accepting my CRPS was that I thought I would have to stop trying to make my CRPS better. I just couldn't see stopping my meds, quitting nerve blocks and no longer looking for better treatments. Who wants to roll over and say "Sure, I want my CRPS to be this bad for the rest of my life!"? I sure don't. Again, that's not what radical accepting is about.
So what am I doing to radically accept my pain? First, I'm not fighting the fact that I have it. Realistically, fighting it won't do me any good. Sure, striving for improvement is important and I still look for better treatments. But I am not fighting. It's not a war, battle or fight. Instead, it's a perseverance, effort or journey. I am working to find a better way of living. In DBT, the saying is "building a life worth living". I've already decided a while ago that life is extremely worth living, I'm just making it even more so. Anyway, as part of that, I'm working to improve my health and decrease my pain, but I'm not fighting my pain. It's a more positive outlook; instead of saying "I'm fighting this", I'm saying "I want more of this and less of that".
Next, I'm saying that my pain is not good, but it is there. It is what it is. No amount of saying "I don't want it!" is going to actually make it go away. Think of it this way. Any Minnesotan knows that winterr is coming. I can wish for 75 degree temperatures, but saying "I don't want it to get colder" isn't going to make it get warmer. It's not going to make it go away. In the scheme of things, I haven't really found that I'm suffering more because I wish for warmer temperatures or think that winter sucks, but then again, I don't go out and bang my head against the frozen lake or something to fight the winter either. I'm not saying I love my pain or think it's good, I'm just saying it's there.
I'm also doing my best to change my outlook on the difference between pain and suffering. In DBT, we say that "Pain creates suffering only when we refuse to accept the pain". I can be in pain, and not suffer. I can be in pain and enjoy life. I can be in pain and have hope.
I hope this helps you understand radical acceptance. It's not easy, it's not something you do once and are done, and I'm not an expert. It is, however, making a huge difference in my life. It's one of the many ways that I've again realized that life is indeed worth living.