----------
The actions of a character are what drives an entire plot. A Mary-Sue would make the right choice (or the wrong choice, if they were evil) all the time for all of the right (or wrong) reasons. No one action works all the time, nor are they purely driven by right or wrong reasons. Characters aren't going to succeed or fail all the time. That's how it is in real life. We all have our own successes and failures, and the characters that we create should be held to the same standard. The abilities and personalities also play into the actions. Naturally, an experienced character will succeed more than an inexperienced one.
Finally, there are the abilities of a character. For every strength, there is a glaring weakness, mainly coming from the strength. Mary-Sues don't have many weaknesses. The worst ones don't have any. Abilities are like a two-edged sword. A character can't have it both ways. There's also the case of a character with abilites that they cannot channel at all (for example, a big, strong bodyguard who can't use the natural power he's been given).
I hope that explains a bit. I'm sorry if it's confusing.
----------
*Hugs for it* Thank you so much, and it wasn't confusing to me. I think I can be able to pull it off alright now, thanks to you and purple_drake. And it's okay about the one-liner, I guess I was being a bit naggy like I can be.
Thank you!
And if you're wondering why I'm not doing it in the club, it's because I don't feel I know how to contribute more to the thread at the moment, so I'm just sending you this message to avoid spam.