For (fictional) example, I just finished reading Neil Gaiman's Anansi Boys. There is this one scene in a karaoke bar, in which the main character is watching this girl, Daisy, sing. She is completely off-key and generally pretty terrible, and he talks about feeling embarrassed for her. Then, when she gets off stage, she is laughing and talking about how much fun it was. She is obviously fully aware that she was bad, but did it anyway simply because she wanted to. All of a sudden, instead of feeling embarrassed for her, he (and I) saw her as this amazing, fun-loving person who doesn't give a shit what anyone thinks of her.
(On a side-note, Daisy actually ended up being my favorite character in the book. She was smart, and funny, and a total badass who knew how to get shit done.)
What isn't charming is someone who does things they are bad at without being aware that they are bad at them. That's just kind of pathetic, which is why I would like very much to avoid it. Basically, I feel like anyone can pretty much get away with doing anything, as long as they have the right attitude about it. If you're doing something that you're good at, you should have an air of confidence about you. If you're doing something you're not good at, you should have more of an "I don't care what you think of me." vibe. I think that's a major reason why I don't do very many things; I don't know what attitude to have about them, and it just seems safer to avoid them altogether.
(On another side-note, what is it with Daisys? They're always so fucking cool! Daisy was also one of my favorite characters from Being Human, and it turns out that Skye (from S.H.I.E.L.D.)'s real name is also Daisy. Perhaps I should just change my name to Daisy, and then all of my problems would be solved.)
^ Daisy Hannigan-Spiteri