There's a sense in which discontent is a trait of a good leader. Good leaders see the things that could be rather than the things that are, and help push others towards the "could be." But as with most good leadership traits, discontent can also bite you on the butt.

Discontent has to be tempered by faithfulness, or it becomes destructive.

You may want to reach the world, but you have to start by being faithful to the people God has brought you. If you're serving at 1st Baptist Church in Podunk, Oklahoma it's okay to want to reach a postmodern generation, but that doesn't seem to be the arena where God has placed you. It's not okay to neglect the people of Podunk in the process. It's okay to want more influence at work, but you can't neglect your current position in your pursuit.

Discontent has to be balanced by faithfulness or you'll neglect the responsibility God has given you on one hand for the dream of what He might give you in the future. Be faithful where you are as you push towards what could be (Matthew 25:21; Luke 16:10).