Managing can be more discouraging than playing, especially when you're losing because when you're a player, there are at least individual goals you can shoot for. When you're a manager all the worries of the team become your worries.
I don't like people who drain my time and energy. If you've seen the Harry Potter films, we use the term 'dementors' - people who can draw the life out of you in terms of your energy. So we eradicate the 'dementors', encourage the positive people, and that spreads around to create the team spirit we have here