Efficiency and effectiveness are not the same. Someone who works hard and is well organized but spends all their time on unimportant tasks may be efficient but not effective.
To be effective, you need to decide what tasks are urgent and important and to focus on these. This is called prioritizing. It's important to list the tasks you have and to sort these in order of priority, and then to devote most time to the most important tasks. This avoids the natural tendency to concentrate on the simple, easy tasks and to allow too many interruptions to your work.