I can't speak for your child of course, but I can give you a little story. My wife and I went to the same schools since kindergarden (not same class) to university, so the topics and difficulty were about the same. She always had fantastic grades (90%+) and she got the encouragement that parents usually do ("You're so smart!", "Ohhh yes, she is very smart, she had a 100% on X"). I on the other hand, was an above average but didn't care much so my grades were just a bit better than average (70-80%) but something my father said always stuck with me "I don't want/need you to be a genius, just work hard." That's about what I remember of my parents parenting technique: "Just work hard".
Now, I'm 29, and never excelled at school, dropped out of University after one year, travel across Europe working as a programmer in many interesting projects and can say I live a normal balanced life. I don't dwell much on problems, and accept that things change and I can change.
My wife on the other hand, she has very low self esteem mostly because she believes that what she does is what she is. She can't change it. If she forgets about something she says she is dumb. If she breaks a glass, she says she is clumsy, and has a very hard time believing these things can change. She is stuck at a miserable job because she is too afraid to move and fail at the new one (even though she had better offers). She can't really separate what she 'is' from what she can become. For her, mostly due to the way her parents praised as a child, she came to believe we are born a certain way and can't really change.
Long story to mostly tell you (though, I'm not a parent yet so I can't say I know what the hell I'm talking about) that as long as you can teach your kid that what we become is product of what we do, and not who we are born, she will probably be ok. Try to find thing you can point to hard work. She does her homework? Nice, then tell her next time she gets a good grade "Good thing you did all you homework, see how it payed up". She may still think it was easy, but she her subconscious will link hard work and results.