Whoa,13 and 8 pixels, how big is your canvas??
Mine is A3 and I never ever use a brush more than 6pix, my standard is 4pix
I think your emotions are pretty on point though! But there's no end to perfection I usually use characters who can have those really exaggerated big mouths, who are smiling wide and shout with mouth full open, not the introverted characters for trying new things.
@migxmeg hehehe, thanks! I actually drew it big, then made it smaller, but then I felt it's just not quite the same feeling. I think when it comes to the emotions (well... and everything else, if I think about it), you should just not be shy about them, even if they look ugly or stupid and unnatural for some time. One of my favorite artists is drawing crazy exaggerated emotions, but when you feel how good they are, you don't care if they are not realistic at all. I'd recommend just finding some crazy emotions (photos or emoji templates by other artists) and sketch those, not minding how they look.