How to get my friends to let this go?

Use short direct phrases and the broken record technique. Eventually, they will get it that you know what you are doing. For example, you can say, "I know what I'm doing." or "Stop telling me what to do, I know what I'm doing." and just repeat the same phrase every time like a broken record. The more you say, the more they can use it against you, so make it simple and direct. Eventually, they will see that they cant rile you up and they will stop.