Being a useful a-hole & a character's great escape

Today I was a bit of an a-hole. That's just how I felt after I submitted my crits. Fortunately, the people I sent them to actually thanked me and said they were very useful and that flattery never got anyone anywhere.
The thing is, I agree (though I do like to get the occasional praise), but I'm worried about how my voice comes across on paper. Do I sound mean even if I don't want to? Can my jokes be interpreted as sarcasm when I was only trying to be funny?
I never mean to offend. I sometimes just get really passionate about the thing I do (in this case critting) and I feel like putting everything into my point to show why I think it's not working. And the better the story is, the more worked up I get. Which is... good?

Anyway, it got me thinking. Can I put my character voice across if I can't put my own? It happened sometimes that cirtters pointed out things about my characters that I hadn't noticed before. And it influenced all my writing of that character from then on.
Someone once told me (recently, actually) that they don't see my character as a damsel in distress - which is fine, I always tend to write strong female characters (unless I don't really like them - then I let them be damsels), but I had no feelings about this particular scene whatsoever. It got me thinking - God, am I losing grips on my characters? Apparently not, since in the next scene she turned into a sappy idiot for a couple of seconds.

I have to admit that Rachel, the MC from my NaNo 2010 project is the first character who ever backfired on me. I had her in mind perfectly, knew who she should be like and what she should do, but she wouldn't. As soon as she stumbled on paper, she turned into the most insecure and can't-make-up-her-damn-mind character I've ever created. Almost, anyway. And she pisses me off because I didn't want her to be like that. I wanted her to be witty and cool and everyone's best friend. Ah, big fail there!

Example(excerpt from Hunters):
[What’s wrong with me?
Daniel turned to her and took her in his arms. “Oh, no, Rach. Don’t do this to me. There’s nothing wrong with you. You’re just special and I can’t figure out why.” 
“But what if…” she sobbed. “What if I’ll never get better and I’ll be a burden for you all the time?” She wished she could stop crying, but this was the worst time to find out she was so weak. Having to depend on someone for defense wasn’t high on her list.]

Now, if this were up to me, she wouldn't start acting like a human hosepipe, get to her feet and start training her butt off to get better (at fighting and stuff since she has to fight and kill vampires). She should get angry at her own incompetence not crawl into the arms of a guy (which I think I did a much better job on). But it wouldn't fit her character now, because that's just who Rachel is - she can be brave - she doesn't want to be a burden and not be able to take care of herself - but she doesn't really do anything about it right now. Maybe she would later, but she won't get the chance because magic happens (I use magic to block out any spoiler alert *evil grinning face*)

Anyway, from my epic fail, a new character has risen, and I just hope another useful, priceless a-hole will shout at her if she tends to get pathetic. Then I will smack her into submission.