The general feeling is, if you don't treat everyone the same you're showing partiality. To me, that's when you show the most partiality, when you treat everyone the same. You must give each individual the treatment that you feel he earns and deserves, recognizing at all times that you're imperfect and you're going to be incorrect oftentimes in your judgment.
You have to work hard, and you have to enjoy what you're doing. If you don't enjoy it, no matter how hard you seem to work, you're not going to be working as hard as you can because you're not enjoying it.
Define success for those under your leadership as total commitment and effort to the team's welfare. Then show it yourself with your own effort and performance. Most of those you lead will do the same. Those who don't should be encouraged to look for a new team.
When you punish your people for making a mistake or falling short of a goal, you create an environment of extreme caution, even fearfulness. In sports it's similar to playing "not to lose" - a formula that often brings on defeat.