I liked this very much Erulisse!

Therefore the banishment only succeeded in tempering his steel, not softening it. 

 Oh yes, indeed. This is Fëanor.

Thank-you for posting this. :)

//Over time, instead of clarity of vision, the imagined insults given to him by the Valar and his half-brother became magnified in his mind.  Therefore the banishment only succeeded in tempering his steel, not softening it. //

I think that's a perfect encapsulation of how it must have been.  Lovely, thank you!