One of the benefits of being a doormat is his generally polite nature; it helps to smooth over the frustration at his self-effacing side. A necessity in situations like this, to keep him from being obnoxious in his panic.

"I-- That came out wrong-- I'm sorry, self-pity isn't helping. It's a good thing that everyone gets one, if these are presents! Right?"
Which is true; if there are others as adrift as him, then the promise of a solid landing is something that everyone deserves. Gordin hugs his things closer to his chest, smiling apologetically for letting his bent towards the mediocre come out in such an almost passive-aggressive way. Steve doesn't need to put up with that after being so helpful already.

"Oh, well...I suppose it's a relief that they're not lying to me straight up; that'd be a bad first impression. I, er..."
Flexing an arm, he laughs with no small degree of sheepishness. "I'm glad that sparring's an option! But...I'm not very good when I'm up close--"

But that's no excuse to not learn how to overcome his melee shortcomings, is it? It's win-win if he can master sparring without pointy flying sticks, and the delight is plain on his face. "No, no excuses; if that helps, then I'll do it! I'll become the best fighter I can!"