Sometimes the best set experiences make for the worst films. So, you don't want it to be too good an experience! But the bulk of your life is working with people and collaborating so you don't want anyone to be miserable on your film either. You want it to be something that people walk away from saying that it was a good experience for them and hopefully a good film. As a director, you are sort of leader of that troupe for that period of time, so you're aware of morale and your effect - how you are as a person and how that sort of trickles down to everyone else.