Bruce Tulgan, founder of the management training firm RainmakerThinking, says that the key to career success isn't only embracing opportunities; it's also declining projects, tasks, and requests for help so you create time for the most value-added work. He explains how to evaluate each ask, determine which you should prioritize, and deliver either a strategic "yes" or a well-thought-through no. Tulgan is the author of the HBR article "Learn When to Say No."