My sister and I have noticed that we cannot simply just "watch" Light & Night. No, we've clocked it at an hour long process. It takes watching, rewinding, musical analysis, character analysis, lyrical analysis, everything. Every single time. And there's always something new to unpack. It's so fraught with things to notice, things to examine, little things everywhere.
Heart is a bitter, resentful, pessimistic person who is jaded by the world around him. He struggles with his depression (or rather, Mind would say he's "ruled by his depression"), and he has very unhealthy coping skills, instead allowing himself to fall into states of numbness (during these states, he wonders sometimes if this is what being Mind feels like, cold and unemotional).
Because he is the emotional side, this makes him a lot more sensitive to criticism, and since "emotional side" means the full spectrum of emotions, he may become angry in response to these critiques, making him lash out, often with violence. Thus the Juno incident.
Mind thinks that Heart is allowing himself to fall victim to his own emotions on purpose, even accusing him of using his emotions to manipulate others. But Heart can't help it, and if he is, in fact, manipulating others, then he is doing it unintentionally and unawares.
Heart tends to focus on the negatives, being the jaded pessimist that he is. He also has a hard time letting go of the past. Thus why when Mind is asking for help during Light, Heart instead elects to focus on their past interactions and fights. He has a hard time accepting the fact that Mind might not actually be the villain that Heart thinks he is.
Despite these flaws, Heart would not trade being the emotional side for anything. Because with emotions come compassion, excitement, empathy, happiness, and the pursuit of comfort. He can even be gentle with those he cares about.
So he just lives with it, lives with the goods and the bads of emotions. What he needs is a balance, a check on his worse emotions and impulses. Which is where Mind comes in. Unfortunately, Heart has a hard time reaching out for help.
He seeks comfort, thus the plushies from my previous headcanon. Being attached to the past, Heart can be very nostalgic.
Sometimes he cares too much, except for when Apathy closes in, and he ends up not caring enough, such as in the end of The Heart Acoustic. Otherwise, his emotions run intensely, as he feels things more deeply than your average person.
(Slaps Heart's shoulder) This guy can fit all the emotions in him.
(All three of these guys have flaws, and the worst qualities of these flaws keep obstructing their points of view. Each of these guys is the problem in their own way.)
