I'm not really the best at critiquing, so I'm going to list what I see wrong and how you can improve. It might come off as blunt but I'm guessing it's what you're going for.
The hand is very small. Generally hands, unless a stylistic choice, should be the same size as the face when stretched out.
Your shading is okay - you have a defined light source and you keep that very consistent and the shading for shape is fairly good as well. The only issue I really see is that you don't use a wider variety of shades and it looks very bland as well as having it lack contrast.
The hair is DEFINITELY your strongest part of the picture - and that's great, BUT, it looks out of place having so much detail next to the shirt which has so little. I struggle with this too, so, I don't really know how to go about giving advice for you because the only thing I can think of is "add more detail to the shirt".
To add onto what Zephyr said about hands, I feel adding lines to show fingers would make it look nicer.
Using multiple shades would very much help the shirt look more appealing, maybe make it look darker in comparison to the hair for some contrast? c: