Literally, a Picture into a Student's Mind

I care about what my students think about me. I've been made aware that I have a bad habit. My bad habit is that when I'm trying to get students' attention or some students are having their own conversation in the middle of the lesson, I sigh. That is, if distractions and acquiring attention escalates high enough, then I will sigh. I don't really get pissed, but I will admit to sighing. I was neglecting that I sigh as a way of expressing my disapproval and at least one student has been observing it. So, she drew a picture, handed it to me, went back to her seat, stared at me, and giggled. Here's her drawing (you can click on it to enlarge it):

When she was giggling at the picture, it kind of hit me where it hurts. She observed a weakness. For me, that drawing and her laughter just kind of rubbed it in. My first thought was that I was annoyed. I wanted to crumple up her drawing and throw it away. Of course, I didn't do that. While Mr. Agajan had control of the class, I was just thinking to myself for a bit. I wanted to know why she wrote it. Right before it was time to go to recess, I asked her if I could talk to her one on one. At first, she seemed really averse to talking with me. She started pouting right after I asked her if I could talk to her privately about her drawing. I simply asked her, "Can you tell my why you drew this?" At first she was silent and wouldn't tell me anything. So then, I followed up, "I care about how all of you see me. If this is really how I look, then I want to change it." Finally, confirmed my suspicion for the reason behind the drawing. So, I followed up again, "When do you see me sigh?" She replied, "You sigh sometimes when you're teaching your lesson." Finally, I said, "Ok. Well, thanks for telling me. I'm gonna try to change that, ok?"

I thought I was pretty patient, but I think I need to raise the threshold of my patience. At the very least, I need to make it less obvious that my patience is being tested. I need to not sigh. Hmmm.... At the same time, I think I might have developed the misconception that if I show my disapproval, they will care. Whatever. In any case, I have nothing to gain from merely appearing bothered. That's undeniable.