A Failure of a Story that I'm not deleting merely for future motivation.

Parties had been crucial to Pinkie Pie before the mane six had split up. Hosting a party, inviting all of your friends to come to the party and seeing all of your friends enjoying themselves with great enthusiasm at the party was Pinkie Pie's form of recreational drug: she relied on it for survival.

As you could imagine, when her former friends began leaving one by one to visit other places in Equestria, Pinkie Pie had something that resembled a mental breakdown. With nopony to enjoy Pinkie's parties, the fuel she hungered for so sorely was not being provided - it began to cause her inner flame to wither out.

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It was only two months after everypony left that Pinkie Pie began to fall into a state of disrepair. Initially, Pinkie went through a stage of minor depression in which she didn't leave Sugarcube Corner or eat a morsel of food once. However, these phases advanced to more serious levels and it wasn't long before poor Pinkie experienced a gigantic and undeserved mental breakdown which resulted in her being referred to Ponyville Mental Institution for six years by the Cakes after they witnessed her mental degrading.

Once Pinkie returned to life six years later, she was a changed pony. No longer was she a cheerful pink pony who caused everyone smiles; she had been replaced by the new Pinkie: a more selfish and nonchalant pony who wanted nothing to do with anypony within her life.

At present day, Pinkie Pie worked baking for the Cakes at Sugarcube Corner. The job was fairly generic and monotonous but that suited Pinkie finely and the pay supported her drab and basic lifestyle sufficiently.

Pinkie wanted nothing more in her life than to be alone until she reached the age at which she must depart her life - she didn't want to help others or receive any help from others.