@Kelli - thank you for the reply.
You have a point.. we cannot expect the managers to actually prepare a stress-free environment for the team. There is much truth in the fact that self-responsibility and accountability reflect on general happiness, at least this would agree with what I observed. Thanks for making me think about this.
Maybe the best thing to do then is to leave as much autonomy to the teams as possible, this way they not only plan their own work for themselves (so no excuses when things get too hard) but also they then are the only people responsible for the actual stress levels?
I might do some testing on this myself :)

Thanks again!