It sounds so simple that people get offended when you say that. Yet it's at the root of a lot of employee performance problems where the employee is doing a lot of activity, but not delivering on expectations.

I've worked with some brilliant engineers who failed because they were always off trying to reinvent the wheel with their own completely unnecessary framework or rewriting some code that didn't need to be touched. In each case their managers were practically begging them to just focus on delivering the tasks they were assigned, but they were still surprised when the performance management actions came along.