When team members become ill or sudden staff changes require additional time for training and deployment, project managers can find their schedules under assault. Most of the time, the effects of outside interference can be mitigated with the same kind of overrun buffers used for dealing with inaccurate projections. However, outside forces tend to require more hands-on intervention, which adds costs and threatens deadlines. Savvy project managers find ways to build cost buffers as well as time buffers into their project plans. In addition, separating project goals into a list of “need to have” and “nice to have” items can prepare teams for the reality of leaving some tasks off the completed list.