From my experience the best impact of worker performance is leadership. This works both ways, poor leadership means very poor outcomes. A leader needs to firstly have a clearly defined vision. Without a vision the workers cannot see an end goal and then it becomes a slog fest for them. Secondly, a leader needs to be animated. The leader needs to inspire their workers to believe in the work, not just do the work. I have been on all four sides of this, good/bad leader and worker answering to good/bad leader. You can clearly tell which groups are going to be effective by the way the leader acts in the first meeting.