When I first learned project management we were really into waterfall concepts like crashing the schedule and EVA. In fact I really enjoyed the process of Pert charts and planning.
But I stated to notice that many difficult things ended up being deferred to “release 2” then “release 2.1” and then “post-release business as usual”. This actually meant they didn’t get done. So I was talking to an experienced PM from a consultancy and he introduced me to the concept of “the peak of expectation and the trough of disappointment”.