Joined downwind the wrong way once. Couldn't work out why the heading on the DI was the same as that of the runway!
Got lost right on the edge of the Heathrow TMA. Called up 121.5 and they were very helpful.
We've all had lucky escapes.
The thing is not making those mistakes but knowing how to avoid making them and knowing how to get out of them if things do go awry. That's what PPL training is all about.