From source:
 
Continuation from my previous work: http://pananovich.deviantart.com/art/Frostbite-goes-on-a-trip-607352961
 
 
Before going on a trip, Frostbite had to deal with an specific issue: Shadowmoon.
 
Both the batpone and the pegasus know each other since fillyhood and had been an inseparable couple by then. They always shared aventures and daily life situations as if they were identical twins that fulfill eachother: her hyperactivity and spontanety is armonized with his precauitonary and premeditation…
 
But they differ when it comes to social life. Frostbite has no issues to travel alone and socialize with (mostly) anyone she meets, but Shadowmoon is more reserved, socially-awkward and has never made a serious-deep conection with other ponys after meeting that bat mare.
 
Leaving Shadowmoon alone at home would have been like leaving a pet dog in a dog pound; he would be so sad that he might die of depression. (this is the only metaphore I could think about while writing this).
 
So Frostbite decided that the best for his “brother of blood from different parents” would be to let him with somepony she could trust while she´s on a trip. She remembered that she met a unicorn that drew a portrait of her a time ago. She seemed to be a good pony after all and maybe she would have no problem to host a pony in exchange of helping her with the house works. The unicorn already told her that her house has an extra room. But to be more sure, Frostbite offered her some bits to let Shadowmoon stay there. The red mane unicorn accepted the offer and promised the would take care of the stallion for her (Did she have another reason appart of the economic one to let an unknown pony to live with her as a temporary roomate? IDK).
 
The same day Frostbite started her trip, both she and Shadowmoon wave off each other and took different directions for the first time in years.
 
He was very nervous but tried to hide it by showing his best smile to the adorable pony that recieved him in the front door and smiled back at him. Until now there was a good first impression.

You should have use past tense.