That would be my theory. Field agents are trained to withstand torture and psychological manipulation and all sorts of stuff, so I don't think he'd have the same kind of PTSD issues Tony -- who's still pretty much a self-taught civilian -- had, or whatever it was Selvig was suffering from (which was NOT any form of PTSD I'm familiar with).

Plus, Clint got to burn off some major energy and rage killing Chitauri, and he got to shoot Loki out of the sky. In his own words, he would probably "sleep better" as a result. Selvig didn't get any of that satisfaction.