Like investments, the ‘best’ productivity tool for you is subjective. It will not be the most widely-used one, or the highest-ranked, or the most expensive one. Instead, it’s the one that is best suited to your situation, and the one that fits best into your working style.
Multitasking is a skill that's often prized in the business world. Companies like to see applicants who exhibit the ability to juggle multiple projects, clients, or accounts at once. How can we, as marketers with many different priorities, manage this conflict in a way that allows us to best serve the needs of multiple stakeholders at once?
Over-commitment is one of those things that serves no purpose other than to kill, steal, and ruin productivity.