Yes, it's normal. Don't stress over it. Ideally you can work on a team or with a partner so that your productivity cycles balance out each other. Probably when

Yes, it's normal. Don't stress over it. Ideally you can work on a team or with a partner so that your productivity cycles balance out each other. Probably when you're feeling unproductive you should just stop working and go do something else; it's better to recharge than to work inefficiently.