Imagining that you lived in the anime-verse, how would you handle a Pokémon with severe depression?

The reason I ask is that I'm preparing to write another piece based on the Ultimate Battle Frontier competitions on Deviantart. This one in particular would involve the same characters from 'Challenging the Blizzard,' but would take place shortly before the 2011 UBF.

The Pokémon in question is Leo's Steelix, Iron Maiden. She was caught as an Onix back when Leo started his journey, and was the first he actually captured. As the years passed and the rogue's journey progressed, she was eventually relegated to the backup roster. It wasn't until recent events occurred that she is finally called to rejoin his main team. Not being used in ages has taken its toll, and Iron Maiden is down in the dumps. Leo wants to find a way to return her to her old self.

Does anyone have any suggestions on where I could take this and how Leo could deal with this situation? And also, what other examples of Pokémon depression have people devised for their own works?