One critical thing to focus on is learning from losing. If you can turn lost rounds into productive time, you will be able to learn from your mistakes, and always take away something valuable from playing. This is also a big factor in maintaining good morale in a team environment. Because you focus on what specifically won and lost in that situation, adding and focusing on your knowledge, you are much less likely to feel angry and frustrated, and importantly you are able to keep your cool and retain something positive from each situation.
There is a critical mass of playing to learn instead of playing to win, and when you reach it as a team, you'll feel this overwhelming change in attitude about the game. You'll feel your reward center change over from being focused on the strain to win, and you'll actually feel reward just from learning.
Play to learn. Turn losing into productive time.
