First of all, your buddy’s story sounds kind of fishy. How would he know that he “flunked” the test? It’s not normal procedure for the person administering the test to actually tell you they thought you were being deceptive afterward. The thing to remember about polygraph tests is that they are not, in fact, “lie detectors;” They are interrogation tools. You can forget about hiding a thumbtack in your shoe or whatever; they’re wise to those sorts of tricks. Your best bet is to just be completely truthful. If there’s something you’ve been hiding, now is the time to bring it up. Your chances of getting hired are much greater if you’re just up-front with the hiring authority from the get-go.
I am of the opinion that it is not good to deceive, even unintentionally. This can create problems for other people, and your loved ones may not believe you. Their confidence in you will disappear. You have to try to tell the truth or watch psychological videos on how to do this. I know it will help, how little but it will help. You can try to do a test with the lie detector, there you will tell the whole truth and it will be psychologically easier for you not to deceive unintentionally, you will be tempted to just tell the truth. You can go to https://liedetectors-uk.com. They will help you!