My DS has always been a "glass half full" kind of child. Prone to anxiety (about school trips, won't go on sleepovers etc), and low self esteem. He has a tendency to think that life is unfair and all the worst stuff happens to him when in reality this is far from the case.
We've been trying a lot of stuff around growth mindset, encouraging him, positive reinforcement etc but he's still stuck in this negative way of thinking.
School work is the source of a huge amount of resistance from him. He's a bright boy and is well behaved at school etc. Brilliant at maths but finds written work harder. But if I ask him to look back over work done to edit/correct he immediately gets defensive and a bit aggressive (in speech, not physically) shouting at me that there's nothing wrong with his work and it's all done properly (when there's questions he's missed out, spelling mistakes for words I know he can spell, etc). I always take pains to show how much he's done well and remind him that everyone makes mistakes etc but it doesn't seem to make a difference.
But today we went up a notch. Having asked him to look over some maths with me where he'd already got 90% correct he got so frustrated that he headbutted the door frame. Where do I go from here? Surely that's not typical behaviour in a child of his age? 
He can be such a funny, loving, kind boy but he's so lacking in either self esteem or resilience (I don't know which) that he can't cope with minor set backs. I don't want him to go through life like this. How do I help him?
Sorry for the long post. I am a long time mumsnetter but have changed my username for this.