Magic is difficult for an Earth Pony, but not impossible.
 
Emmet was convinced that time travel was the only way to save himself from all the torment he was put through. He had heard of other non-unicorns performing magical feats, and so he threw himself into the study of magic. He was obsessed. He would succeed where powerful unicorns had failed and change history.
 
And he did succeed.
 
For the most part.
 
The blast of magic he experienced while time traveling was more than his body could handle.
 
He landed in the past, as he had intended… But not entirely unharmed. Pieces of himself were missing.
 
Whether he was aware or not… something had been set in motion.