Actually it looks like you scaled it up from a smaller size.
But yes, just working neater should help. Pixel art is about pixel-level control - that is, understanding the purpose of each pixel. Messiness means a lack of that control, and a lack of control is much more obvious in pixel art than other media because even one pixel that isn't well-places can dramatically change the look of a piece.
It looks like I scaled it from a bigger size, i know. But I did it in size 64x64 ;-; I should draw it a little bit more neatly. I've just been messy.
But thanks, I really appreciate Your comment. Next time I'll do my pixel arts better ^^
Did you by any chance pixel this and then upscale it? It looks very jagged, and it looks like the sort of jaggedness one gets when upscaling.
If you did upscale it, you should post the original 1x version instead.
Thanks for Your advices, really.
And yes, I know that one pixel can destroy everything I've experienced that when I made a running animation and the outline wasn't closed D: in the game it looked more than terrible, but I have fixed it. I should upload more from my artworks, this little avatar was created because I was bored and just made it for fun.