This is totally me. I create code that will easily handle changes for months and years vs. being able to move the story across the board and say it's done in 2 weeks and then you can't build on top of it because it's not robust enough (but it's "done" and management is smiling). I've lived long enough that I know in 6 months no one will remember if this was finished within the sprint, but I'll sure as hell know if I'm working nights and weekends because I did a crap job to fit it within a sprint.