I used to be happy. I used to be able to run and play in the sun all day. I used to have friends. I used to stay up late telling scary stories with them. I used to love learning all I could. I used to have the greatest teacher known to ponykind. I used to have a home.
I used to be a pony.
Half of me misses my old life and longs to return. The other half demands that I stay. And if...if THAT hadn't happened, I would be able to return home.
I hate my own existence, yet I have continued to do the research I began unwillingly. I've spent days and nights torturing myself over my work. When the pain becomes too much to bear, I go to sleep. When I wake up, I find myself in a new environment. But I'm still the same. I pick up my work again and the cycle repeats.
Despite my wretched state, I'm not the one who has suffered the most. Hundreds of ponies – earth ponies, pegasi, and unicorns alike – have been through excruciating pain dwarfing mine. At the end of it all, their memories are wiped. I pity them, but also envy them. They don't remember anything about their former lives, but I must cope with what could have been. And to my sorrow, my research is conducted upon these poor, poor souls.
But life goes on. Days turn into weeks, weeks into months, months into years. All filled with screams of pain. I look back to my physical torture. I look at theirs. And I am mortified.
I once asked why. I was never answered, but I already knew the answer.
Why do I do it? Because I must.
Why must I do it? Because I can.
For science.

Universe based on My Little Portal