Nearly two-thirds of professionals write to-do lists, but 41% percent of all to-do list items never actually get done, according to research from the project-tracking software provider iDoneThis. In fact, more than half of people write things on their to-do list on the same day they do them.

While to-do lists are popular, they can derail your success, says Kevin Kruse, author of 15 Secrets Successful People Know About Time Management. "Do you really think Richard Branson and Bill Gates write long to-do lists and prioritize items as A1, A2, B1, B2, and so on?" he asks. "To-do lists are where important tasks go to die."

In his research on productivity and time-management best practices, Kruse interviewed more than 200 billionaires, Olympians, straight-A students, and entrepreneurs, asking for their best advice. "None of them ever mentioned a to-do list," he says.

That’s because to-do lists tend to have three major problems, says Kruse:

1. They don’t account for time. When there is a long list of tasks, people tend to tackle those that can be completed quickly in a few minutes, leaving the longer items left undone, says Kruse.

2. They don’t distinguish between urgent and important. There are no time boundaries on to-do lists, and important things often get overlooked. "Our impulse is to fight the urgent and ignore the important," he says.

3. They contribute to stress. Known as the Zeigarnik effect, people tend to remember incomplete tasks, and they lead to intrusive, uncontrolled thoughts. This list of undone things contributes to insomnia, says Kruse.

WHAT TO DO INSTEAD

Kruse found that most high achievers live and work from their calendar. The key to success is adopting three practices that turn your calendar into an effective blueprint for the day:

1. Time-block the most important things. Don’t let your calendar fill up randomly by accepting every request that comes your way, says Kruse.

"Get clear on your life and career priorities, and preschedule sacred time blocks for these items," he says. For example, you might block off two hours each morning to work on a strategic plan or other project that moves you forward. Shut off email, put your phone on airplane mode, and focus on pure productiveness.

Your calendar should also include time blocks for things like exercise, date nights, or other items that align with your core life values. And Kruse recommends blocking time for less important things that you’d like to do, but restricting them to a set amount of minutes. Take calls for an hour a week, for example.

2. Think in 15-minute increments. While most calendars create a default setting for an appointment at 30 minutes, Kruse recommends changing that to 15 minutes and closely evaluating how much time a task will need when scheduling it.

"Ultra-productive people only spend as much time as is necessary," he says. "Yahoo CEO Marissa Mayer is notorious for conducting meetings with colleagues in as little as five minutes. When your default setting is 15 minutes, you’ll automatically discover that you can fit more tasks into each day."

3. Schedule everything. Instead of checking email every few minutes, schedule three times a day to process it, says Kruse. Instead of writing "call my sister" on your to-do list, put it on your calendar. "Better yet, establish a recurring time block each afternoon to return phone calls," he says.

That which is scheduled actually gets done. "When you are forced to pick a specific day and time, you will get the right things done on more consistent basis and your stress will go away," says Kruse.

Kruse admits that it can be hard to estimate how long things will take in the beginning, but with practice, it will become easier to stick to your schedule. He also recommends scheduling some buffer time, such as a longer lunch than you know you’ll take, or time at the end of the day to wrap up work.

"Unexpected things will come up, like getting a call to pick up your daughter from school because she’s sick," he says. "And if nothing comes up, you can use the time to get centered, relax, or think creatively."