It's tough to pick just one trait to get rid of... I have more bad traits than good ones, in all honesty.

If I was to pick
just one trait to get rid of, it would be my pride. In the past, I never really thought of how prideful I was as a kid, or how arrogant. Especially when people would tell me, "You have low self-esteem!"
They were wrong.
It's quite the opposite, in fact. Deep down, I'm convinced that my way of doing things is the RIGHT way. My way of thinking is the CORRECT way to think. So when people criticize me, or say or do anything that challenges that idea, I get really upset. Like, REALLY upset. I complain that they're the ones that are wrong, or I complain that I wasn't told right to begin with, or I throw a fit and become despondent. Thus, I have a hard time improving as a person. On a thinking level, I know I'm wrong and I need to accept criticism, but I hate hearing it, or thinking about it. :E
Now, if I could pick other traits to get rid of, I'm horrible at articulating my thoughts, and I have horrible social anxiety, making it even harder to articulate my thoughts to people, particularly boys. So, I'd get rid of those. And I also have bad ADD, and I have anger problems. Laziness is also a HUGE vice for me, as well as procrastination (or is that redundant?). And I eat way too much.