Susanne: Hey Peter! How is your new workout plan going?
Peter: Not so great.
Susanne: What happened? You seemed so excited about your New Year's resolutions last week, saying you were going to go to the gym four days a week.
Peter: I had dinner plans after work on Tuesday and Wednesday, and then on Friday, I was so tired. So it's back to the drawing board on my resolutions.
Susanne: Well, two days isn't too bad. Can you plan to work out on the weekends?
Peter: I was hoping to have my weekends free, but I think I might plan one weekend day each week. Then I can plan to go to the gym two days during the work week, making it three days a week.
Susanne: That sounds pretty good to me.
Meaning: When someone says "back to the drawing board," it means that a previously established plan isn't working and that it is time to re-plan. In the above example, Peter's New Year's resolution doesn't work with his schedule, so he needs to re-think his resolution and come up with something that is actually possible. Sometimes "back to the drawing board" will be used in a complete sentence, such as in the example above; however, the idiom will sometimes be used on its own, as in the following example:
Lisa: My job interview went horribly!
Jason: What happened?! I thought you said you were perfect for that job?
Lisa: I thought I was, but then I got to the interview, and the interviewer started asking me questions about things I didn't understand. I was so confused by his questions, I finally just told him that I misunderstood the job qualifications and apologized for wasting his time.
Jason: I'm sorry to hear that. What are you going to do next?
Lisa: Back to the old drawing board, I guess. I thought this job was so perfect, I didn't apply anywhere else.
Jason: Well, good luck in the new job search!
Meaning: This time, Lisa uses the expression "back to the drawing board" without a subject and verb in answer to Jason asking "What are you going to do next?" suggesting that she is starting a new job search. Also notice that she adds the word "old," which is common with this expression. The meaning does not change when you add the word "old."