i'm the best

Over the past few days, Jem has experienced a surge in confidence. It started out with his lego- building skills. And this morning, while we were coloring at the table, it progressed to include coloring, playing computer games, and cutting things out. In Jem's own words, "I'm the best at all of that stuff."
So now I'm in this quandary of how to handle this. I want my kids to be confident. I want them to have some pride in the things that they work hard for and achieve. But confidence can so easily tip over into arrogance and I definitely don't want that. How do I teach my kids to be confident, to acknowledge their abilities, without bragging or being prideful?
One option could be telling him that he really isn't the best at all of those things but that didn't seem like the way to go. Instead, I tried to temper his bragging in two ways. First, I asked him if he could name some things that Truett was really good at. I thought that thinking of other people's gifts might help take the self-love down a little bit. He wasn't able to come up with anything that Tru was good at. Not surprising.
So then I thought I would ask him to name a few things that he wasn't as good at, things that maybe he needed to work on or practice some more. I was thinking of actual activities, like swinging a bat at a ball or recognizing sight words. He thought I was asking about behavioral things and told me that he could work on being a better listener. (Right answer, wrong time)
Eventually, I just let it go and reminded both boys to only say things that they would want someone to say to them. If it continues, then I guess we will have to have a chat about bragging. Until then, I will just have to hope that he only feels confident enough to say stuff like that at home.