I really enjoyed your assessment of slack, and it made me reflect also that the multiple Jesuses may be a deep way of thinking about the Trinity ...

Re: "It is the willingness to cast aside very serious obligations because they do not actually serve what you want or need."
The idea that there are different forms of serious obligations - those you want/need and those you don't (which may be chosen for other reasons) - is key to obtaining slack. Perhaps Zvi's binding constraints of behaviour should really be unchosen binding constraints of behaviour.