Pinkie Pie is always looking happy, and reacts to even bad news with comedic overreactions. It all seems pretty forced, exactly like how I hide my own depression. She's not my favorite pony, but the ever strengthening headcanon of her cheerfulness being a facade is making her the most relatable one.
We've all seen how the normally cheerful and energetic pony turns into a practically different person when her negative emotions reach a breaking point. I think that might be the real Pinkie Pie, the one she tries her hardest to hide behind a mask of two-dimensional lolrandom partypony. This is exactly what I do in my own life, where I must keep a permanent smile on my face or else I break down and everyone sees what a miserable human being I really am. Of course everyone says that you shouldn't hide your feelings, but it's obviously a lie as honestly saying that they don't like downers and will stop being friends with them would make them look bad. So, Pinkie, like me, puts on a cheerful face because that's the only way to conceal the horrible sadness inside.
What do you think?