re: estimates: This is equivalent to saying don't confuse estimates with delivery dates, which I wholeheartedly agree with. But you also have to be willing to

re: estimates: This is equivalent to saying don't confuse estimates with delivery dates, which I wholeheartedly agree with. But you also have to be willing to say "The estimate was wrong, here's a new one" sometimes. re: sprints: You don't need a barrier against "can you do this thing". If the thing is important enough, do it; if it isn't, don't. You work on whatever the top priority is, and your sprint commitment is just a list of what the priorities were, N days ago. (Edit: you do still need a PO willing to say "doing the thing would delay the other thing" though)