Acknowledge (and Learn from) Failures
As a programmer you will do things wrong. Maybe you underestimated. Maybe you misunderstood requirements. It's important to be honest with yourself and stakeholders, and take failure as an opportunity to improve.
Telling people what they expect to hear just defers the inevitable.
This applies to large things like iteration reviews as well as small things like looking over some code you wrote yesterday and realizing that it was not as good as you thought.