There are several things that rise up in him to say -- I care more for thy joy than my own, or perhaps Thou canst learn a thousand things, but I am meant to be good at only a few. It moves him to hear that Laertes desires Lancelot's joy; there's a little moment of pain as he realizes that he does not expect that from anyone, even if he knows his happiness matters to them. He realizes that he still expects, first, to be required to bring joy or be pleasing to someone he loves. (Not that Susan has given or held him to such an expectation.) He expects, at his core, that he will need to please them in order to be loved in return.

It shouldn't be surprising, but it is, at least a little. He takes a breath, scrubs a hand over his face, and says, as cheerfully as he can manage, "I shall try that, then."