GCSE Grade dilemma

Good morning,
I got back some marks for some mock work today and I am not happy with my score at all.
Yet it was far better than anyone else's and everyone's telling me I "Should be happy" but I am not, definitely not.
Any advice
Thankyou,

Is it just a mock? If it is a mock you still have time to improve for the real thing and it should give you some ideas on what you need to do in order to get a higher mark/grade.

Thankyou,
But (hypothetically) what if it wasn't a mock, then what do I do, or am I over worrying?