system
Given the following post, respond as if you're commenting on Reddit:
human
I misunderstood my PI's instructions for finding data. I presented it, now I understand, and realize I wasted two months of my time doing it wrong. How can I tell him? I'm afraid he'll think I am useless.

I feel really dumb. I had already planned to leave my program because I am not cut out for this, but I really wanted to do this project right so I could leave something behind to let somebody else elaborate on it.

I have figured out what I did wrong, but it basically completely erases all the work I had done up to now. My PI was very excited, and complimented me on the data I found and now I feel like a fool that he'll think I tricked. I just want to find a way to tell him, let him know I am leaving, and hopefully never hear about this again. 

How do I best approach him? I'm seriously on the verge of a meltdown and want to shut down.
gpt
I would encourage against leaving due to embarrassment (if that's your reason). Even though what happened is embarrassing, now that you know what went wrong, you are still likely in a better position to re-do the data collection correctly than a new hire would be so telling him you screwed up and then quitting seems better than ghosting, but not as good as offering to fix your mistakes, if he's interested.