Board Thread:Naruto Discussions/@comment-31278419-20170331010234/@comment-734582-20170522170710

I don't think the Curse of Hatred was meant as a literal curse. Rather, the circumstances and power of the Uchiha would always lead them to hatred. It's implied several times that the Sharingan gives photographic memory. But the fading of memories and the lessening of pain are essential to processing things like grief. With a perfect memory, every time you remember a painful event would be like experiencing it like the first time.

Couple this with the Uchiha's great power that they were never able to transform into an influence in the world and the prejudice from Indra passed on in each generation, and each Uchiha is far more likely to go insane while getting enough power in the process to do a lot of harm.

The curse of hatred is broken because Sasuke is the last Uchiha, and so by reforming Sasuke the clan is reformed, and so the future members are freed from the pain and anger previously passed on.