"...I can't ride you?" Link says, disappointed. He doesn't want to do something the reindeer doesn't want, but...it's a flying deer!

Until this moment, 'ride a flying deer' wasn't something Link had known was something he wanted to do at least once in his life. But then, he hadn't known it was an option before. Now it is, and the thought that he might not be able to do so is mildly crushing.