collaborating is an amazing experience that is A LOT of work to get right.

absolutely. It's wonderful when it works right, but it's too easy to hurt someone's feelings or make them feel slighted or just dissatisfied. And that's the last thing you want, isn't it?

I'm lucky that Leah's extraordinarily thoughtful and gracious, but not everyone has that mode as their default setting, so it's probably a good idea to agree on boundaries and how you and your partner would be comfortable working together. Then you can relax and have fun writing cool fic together!