Thinking on it, I don't think Germany should be so happy about this result. Of course there is a confidence boost in winning with such big numbers in the quarter finals, but it can also breed arrogance and overconfidence in your abilities. Especially since the result wasn't so much due to Germany's play, but due to Brazil's complete meltdown. And it's not like either Argentina or Oranje won't have confidence after reaching the finals, it kind of comes with beating everyone, after all.
What's worse for Germany is that they had a terrible prep for the final, they had a match against their weakest opponent of the entire tournament, which is terrible training for tactics, teamplay and creativity on the pitch. Germany got nothing out of this match, all they had to do was get the ball near the goal and score, as if they were playing a bunch of kids on the street for fun.
Also, although this is marginal at best, the crowd will be heavily favoring whoever of the two countries they're facing, just because the German team humiliated theirs so much. There is something to be said for getting a boost by being cheered loudly by a crowd and having your opponent hated with a passion.
All in all, great result for Germany, but I think they would have been better off with a heart fought 1 or 2 goal victory.