Because she's just THAT positive and that strong... Pinkie's an incredible character (that's why she's my fav pony). Although, I definitely agree with you on what you said, she can have bad moments too, and same goes for me, I'm kinda like Pinkie IRL, always so positive and smiling, but I do have my bad/depressive moments... So yeah, gotta love this artwork ^.^ Thank you for this.