He folds his arms in front of his chest and makes a noise that clearly states that the question is complicated.

"I vowed to prove I could change only for the person who I wanted to prove that to, to leave at the last stop. Now I simply am continuing that practice simply because it would be a waste of effort not to."

In other words he is disappointed but despite himself he still holds out hope that someday Xingchen will return and his efforts won't be for nothing.