i seem to have a lot of strumming questions. i heard when strumming your aren't supposed to have a stiff wrist. but for some reason that always happens to me. lol it sucks being away at school trying to learn guitar by yourself. i guess i've picked up a few bad habits
it helps if your wrist is relaxed. if it isn't then you end up playing with your elbow, and we don't want that. don't give up learning by yourself. a lot of players do that, and they play just fine. good luck man
Keep it loose. Like try to have NO tension anywhere in your arm. As for the wrist motion think of it almost as if you are shaking your wrist but more smoothly, like we you hurt your hand and you shake it off cuss it hurt, but only not so erratic but that general motion if that helps.