This context comes from the movie "Five Easy Pieces"
BOBBY-What're you doing right now...
CATHERINE-Right now I'm going to run a hot tub and soak myself.
BOBBY-Then after that?
CATHERINE-After that, I plan to read some music and rest for a while.
BOBBY-Tomorrow, then.
CATHERINE-Tomorrow's a full practice day... But the day after is kind of open.
"full" at TheFreeDictionary.com:
- (often with of or with) bursting, packed, teeming, abounding, jammed, swarming A day full of entertainment.
If it says "often with of or with" then it means that it sometimes occurs without it. Does the sentence mean essentially "Tomorrow's a day full of practice"?