Competitiveness -- Wren, my ds is ridiculously competitive. He's grown out of it somewhat (he's 5), but it's still there. To work on it, we taught him the word "persevere," and it's a word we use at least 5 times a day at our house. If he's struggling or losing at something, we ask him what he needs to do to succeed -- and he knows he needs to persevere. He's been much more willing to try with a word to describe the effort in a positive light.
As for outright losing -- for that, all we do is the standard "Did you have fun playing? Well, good! We play to have fun, and we usually have fun whether we win or lose -- but it's really fun to win, isn't it?" That's actually worked quite well after about a thousand repeats.
Or maybe he's just outgrown it somewhat, I don't know! It is extremely normal for children that age, gifted or not, to be upset over losing. We all know it is more fun when you win.
