Dak Prescott clearly ain't letting his horrific injury get him down ... the Cowboys QB posted a smiling update Thursday -- vowing to come back stronger than ever.
"This little adversity is just going to be another chapter in the book," the Dallas superstar said. "And I'm excited to move forward and write it."
Prescott had surgery Sunday night to fix a dislocated and fractured ankle ... and is expected to need at least 4 months before he can get on the football field again.
But the 27-year-old -- who was on his way to see his leg at the doctor's office for the first time since his operation -- said in his video update he's "in great spirits.