You need to learn when your body needs a break and when you're just making excuses. I've had many nights when I've felt like blowing off class due to work, kid, life, etc. Typically, I find this feeling lasts until the first ukemi. Then I get this rush of energy that carries me through class and well into the next day, and makes me wonder why I ever considered blowing off class.
No one will come to your door and force you to go to class, but your skills won't develop as quickly while you're not going either.