It's a little of both. [She rubbed her arms a little.] If we don't already have something available, we have to make something new. Sometimes, the spells are old and hard to remember because of old words, but the newer stuff and the stuff we make on our own is usually pretty easy.
We do have to be careful, though. Just writing anything can have unintended consequences. Especially if it's more self-serving than helping someone else.