Perpetual optimism is a force multiplier
I think we've all realized that mood is contagious. If the most visible person in a group is happy, then the group starts becoming happy. If the most visible person is one who "whine and blame engender the same behaviors among their colleges:."
In many cases it is all about perspective. I once was evaluated by my boss saying "Matt, you don't get stressed enough. This project is millions of dollars, and the problem is thousands." The bosses issue was that I wasn't freaking out from the delivery issues. In truth, I was working hard toward getting it done, and my attitude got other people to jump in, and we fixed the delivery issues before the last rig was delivered.
But a large part of the reason I could do that was my background allowed me to look at the problem as a problem, rather than a crisis. My military background taught me that a crisis means bullets flying, bombs going off, and/or the potential for loss of life, limb, or senses. If that wasn't an issue, it wasn't a crisis. So I would take a look at the situation, identify how to move forward, and moved in that direction. Because I didn't get upset or panicky, my team worked with me and we got the job done.
Of course, not everyone has that perspective. The real trick is to get that "gung-ho" attitude and keep it. Remember a leader is about showing confidence and optimism... a lot of the time, even when you don't feel it.