Should I cancel my pass if I'm not going to attend?

You should cancel your Discover & Go pass if you are not going to attend. Otherwise, once the date passes the system will count it as a used pass. This also frees up the pass for availability to others. You can cancel your pass up until 11:59 p.m. on the date the reservation is good for.

Here is further information on canceling passes: https://youtu.be/DT8ayGjefAU