In a way, Envy considered a door to be much more of a father to him that Hoenheim of Light ever was. He loved and hated the Gate, just as most of those who knew of it did; not understanding it, but fearing it's power; hating the existence it had given him, but being terrified of the very concept of not existing at all. The Gate had taken the alchemist's offer, arranging human components with the hands of it's millions of tiny collectively minded creatures, and spit out the sick caricature of a living thing, every gateling grinning as though it were some great joke.
The thing that became Envy couldn't think straight for it's first moments of non-life, in the midst of the pain of birth and the searing sillhouettes of memories that could never truly belong to him. Pain was all he could feel, as the horrified human backed away and ran from the sight of the abomination he had made.
Loss...
The sound of a door closing was all he could hear; another memory seared into his tortured and unstable mind. That door closed a valve in what would have been his heart, had fate been more generous, and allowed another small passageway to creak open, the trickle that grew into a torrent.
The sad creature could only resolve to hate. Losing love was more painful than being slammed inside the closing doors.