Actual vs. Estimated: You cannot optimize a schedule you don't accurately measure.

For one week, do not just look at your "To-Do" list. Keep a notebook next to your mouse. Every time you switch tasks, log exactly what you did. You will find that "15-minute" email checks actually take 45 minutes of "re-focus" time.

At the end of today, compare your planned schedule to your actual work. If the overlap is less than 70%, your "System" is a fantasy.