It goes like this: if you knew that you had to eat a frog, you would most likely delay that task on your to-do list until the end of the day. However, you would be filled with frustration, anxiety and distraction as you worked on your other tasks rendering you less productive.
The solution: eat the frog first. Deal with what you don't want to deal with on the front end and get it out of the way. Once its checked off the list, you will be more effective and productive throughout the day.