Once you’ve cast off, you’ve got a finished tube of fabric. For a hat, just sew the top shut with a yarn needle. For a scarf, congratulations—you just made a very cozy tube scarf that can double as a neck gaiter or a very long sock.
And if you messed up? No one will know. Wear it backwards or call it a “deconstructed design.” Yarn is a very forgiving medium. It’s not like carpentry—you can’t cut off a finger. (Unless you’re using a loom with pointy pegs, in which case, ouch.)
So go forth, cast off, and remember: the only thing you’re actually casting off is the fear of finishing. Your loom may tremble, but you are the boss of this yarn. Now go make something—or at least go have a snack. You earned it.
