That's a good point, "I know that when I play tennis, I just can't for the life of me care when I lose." I'm similar, funny enough. I enjoy sport, but competition stresses me too much to get fixated on. It comes in waves but I'm not a super-keen hunter of scalps. And I think in that sense, natural temperament helps, but it isn't the whole picture. Somebody who maybe naturally unflappable might be great in the clutch - or they maybe too laid back to care.
It could be that Tsonga is training harder at the mental side than anyone, but I never saw any signs that he's prepared himself mentally. You often see a guy step up at moments where he recognises his usual achilles heel, but with Tsonga, it's like he turns up already beaten when there's a truly great chance to do something big. He beat Federer in the QF of Paris, then didn't look like he was in the stadium against Ferrer in the semi. I realise that Ferrer is better suited to clay, but that didn't explain JW's complete inability to cope with the moment.
A lot of it could be fan mentality too. Look, we compete vicariously through these players, right? We get bragging rights when they win, and face the gloating of others when they lose. And yet, both sets of fans are sitting watching television, contributing absolutely zilch to the actual process. So as fans we have our preferences, and mine have always been for players like Rafa, Pete, no fuss, brutal in the clutch, no vanity. Bjorn Borg. These guys have superhuman abilities to focus down to the core when there's hot flames all around them. So I'm naturally disposed to dislike the Monfils sort of guy, who plays trick shots when he should be concentrating on closing out the set and getting ready for the next one...