I'm going to nitpick things, just to point out what to improve on.
- As you can see the 2 ends of the hair will not meet evenly, which will do a cut in the back that looks rather ugly.
- I can tell that the mouth is a too low.
- The hair is a bit strange, very geometric. You should look up references on Google for anime hair if that is what you were going for.
- The stroke on the eyes is a bit too thick.
- The shading (providing it shows on the sphere) will also be cut, as the right side has a significant height difference than then left side.
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But don't get discouraged because once you get peoples opinions, either good or bad, you can take it and implement it into your next texture. If you keep at it and if you are really determined to be a better artist than the skill will show eventually.
Just remember it takes lots of time to be proficient in something.