Be careful what you wish for...

[The Elf-warrior]

I wish Legolas had been named High King because of a mistake by Gandalf

Your wish is granted. But when he announced that he was engaged to Mary-Sue his royal council gave him an ultimatum: either cancel his engagement or abdicate. Legolas abdicated and moved back to Mirkwood with his bride. Aragorn became the new High King. But King Thranduil disinherited Legolas, who moved to Ithilien. He sailed to the Lonely Isle twenty years later after Mary-Sue was killed by a hunter who thought she was a wild cow.

I wish that Turin hadn't married his sister.