Teaching kids to deal with frustrations.

Hi Everyone.
I'm just wanting some tips and suggestions on how to teach my 5 year old and 11 year old boys to deal with frustrations that result in tears. For eg; if they are losing on a computer game, they will get to the point of tears, and even if I suggest they take a break and come back to it later, they won't listen. They continue to play the same game and get more upset. In the end I will usually force them to go do something else for a while. But I want to be careful not to punish them for their feelings, I want to know how to guide them to work through the feeling themselves. Any advice? Thanks in advance!