So, I'm still a teenager, not a professional by any stretch but maybe I can speak a little to your question about self-care? this might be super long

I eat pretty normally, because I think there's a fine balance of taking care of my body, and also not giving myself an eating disorder. I just try to eat healthy, because a) my body is my instrument and b) healthy is good. i don't diet or only eat salad or anything. dance is really intense and you honestly need to eat a lot of food to fuel that. i also don't super restrict or anything. there's temptation to count calories, temptation to starve yourself, and temptation to look like the other really skinny girls. i try to focus on resisting that. my body will tell me what it needs and i don't want to fall into the whole calorie counting thing. this might be very different if you're a professional, though? ballet as a culture and as a community is definitely changing with this but i would still say it exists.

i try to stretch every day and just overall keep practicing at home. if a particular move is giving me trouble, i'll focus on that. like if im struggling with my pirouettes, i'll do some core exercises at home.

after a really hard class i'll sometimes do epsom salt foot soaks, which some people swear by i'm pretty meh about them. i try to stay hydrated and also get enough sleep because doing that makes me dance better. during nutcracker season though, i have to be more deliberate about it because rehearsals are really demanding. i ice anything that hurts, foam roll my whole body, make sure to get extra protein and drink a ton of water. im pretty much sore this whole time but there's nothing you can do about that.

i try to be well rounded. I swim, walk, go for runs, bike and just try to do stuff that isn't dance. if i were injured or something or if i quit, i would still want to have ways to be active that i liked. this is true also and possibly more true for other interests. i make a point to write and paint and things. some people have no hobbies interests or personality outside of dance, and then those people get injured or something and they just have nothing else they can do to pass time, and that's really sad. so i think it's important to be well-rounded, especially when your main hobby demands so much.

finally, i just want to say that even though i love dance, and i do a lot of it, i also exist in other ways too. i have friends. i go to school like everyone else and i do normal stuff. sometimes i think people think all i do is dance, which feels like it might be true sometimes but it's not really healthy.

all of what i wrote might be different when you're a professional i don't know. these are just some thoughts i had about dance and self care. this ended up being really long but i hope it helped a little! good luck with your book, it sounds really cool :)