When you're first creating your tasks, your estimates may not be very accurate, but that's okay. You will learn from experience and make adjustments. For instance, if you estimate that a task will take two hours, but after working for an hour you realize that you're less than halfway done, you should add more time to the task.

Do this by opening the task and adding more time to the amount you still need to complete the task. If you have similar tasks in the future, go to your task list and find the category the task is in. Select all the tasks in that category and adjust the time needed for all of them. This way, you'll have more accurate estimates going forward. Remember to check your cushion to ensure you still have enough time to get everything done on time after you make your new estimates.