Proper, grown-up coding on a business application is incredibly wearying on the mind, and results have shown time and time again through research studies and professional management that past 8 hours coding in a day the average programmer's code quality starts to deteriorate. Past 10 hours it goes negative - at this point the code base is actually being damaged.

"doing what needs to be done to fulfil the promise" is actually alerting the team that you've made a poor estimate of the effort required for this feature and need to recalibrate. It is absolutely not sticking with your poor estimate and delivering shoddy code to the project.