Oh maaaan. I keratin straightened my hair for years because my waves/curls were just completely unmanageable. Luckily I've gotten enough of it grown/washed/cut out that my hair can hold a curl again, because I totally missed it while it was pin straight. I finally have my crazy thickness back and the texture lets me hold my curls for 3ish days now. I can't believe I ever hated my hair before ;_; I was so dumb.
I know some people with like, insanely straight hair have had luck with straw curls, but it looks hella tedious.