Closely related to the concept of saying "no" effectively, is the concept of saying "yes" realistically. I have seen countless instances where DBAs and similar IT professionals will commit in meetings to timelines that seem OK at first glance, but when considered in context of other planned and unforeseen work, cannot be met.

The reason this is so prevalent is, in my view, related to a "problem avoiding" psychology. Many people want to avoid being seen as unhelpful. In a meeting situation where your boss and other bigwigs look imploringly at you to come up with the goods, it can be awfully hard to commit to four weeks instead of two.

The best DBA I know often comes across as difficult in meetings because he doesn't like giving an answer on the spot. But his deadlines once set, are nearly always met, and he generally delivers what he commits to.