AN: A quick little one shot I wrote up on my phone during a road trip, regarding Cas learning what it is to be human. Set to "Middle of June" by Noah Gundersen.

Castiel could remember a lot of instances when the tiny hunter had expanded his knowledge of human emotional behavior, therein aiding him in classifying and categorizing how to respond to certain situations where he would have been defenseless during the beginning of his time on Earth. Being a celestial wavelength minimized the emotion reacting within an angel, as they are pure energy, and therefore cannot be altered.

He remembered the first time they'd conversed and she'd snapped at him- snapped being the only word he could conjure to relate to the whipping force of her words, meant to crack against him. He'd felt a warmth burn off her soul. At the time, he had the intellect to realize questioning the dangerous force was not an option. Later, however, he did inquire upon what she had been 'feeling' at the moment of her fiery snapping. She had laughed at his obliviousness.

"That was anger, Cas. I was irritated by my under appreciated work for the angels I consult with. So, I lashed out in hatred. Sorry about that, by the way."

"It was not of import. You are forgiven."

If he were to be brutally honest, when questioning on humanity, The tiny one was much clearer on the topic then the rest of his humans. Sam was too technical, it never allowed Cas to expand his understanding to a more human depth. Dean wasn't always the best at speaking of his 'feelings'. So when once again Cas appeared oblivious to the scene unraveling around him, he called upon the quickly-becoming-familiar girl for an explanation. This particular scene was increasingly saddening.

Dean hovered over a young woman, laying in a pool of her own blood and sickeningly white. He was pressing his hands to the center of her chest, pushing hard against her chest cavity and forcing her heart to pump blood through her veins. "Come on, come on!" Dean growled under his breath, "You're going to make it!" Bright eyes were watching Dean sadly. Her fingers clenched and unclenched around the sheath of her machete, where the blade had long since been put away after the fighting had stopped.

"I don't understand." Cas said quickly and hardly, clearly disgruntled by the fact. "She is obviously dead. Her pulse has been nonfunctional for the previous two minutes. Why is he informing her she will be revived?" He could feel upsetting waves of tension that seemed to have a hard time clenching and sometimes smoothed into a static-like panic rolling off of Dean's shoulders. He was hushed softly.

"Denial." She whispered. "He doesn't want to believe that he has failed her. We don't have the numerous facts of human life memorized. A few minutes ago, he couldn't bring himself to give up on her, because he did not want to accept the inevitable." She watched Dean's hands stop, and he pulled them back to rest limply in his lap. "Now he understands, and the denial is gone. This is acceptance."

Cas nodded slowly, his deep blue eyes inspecting Dean's form while he felt the fighting static drain to a hopeless little hum.

He remembered the good emotions too. The simple emotions that could be taken in stride were easiest to learn. Happiness was a swelling warmth that gravitated inches off the skin, giving off heat to the surrounding area. When he'd felt her happiness, it was quite similar to Dean's- she was drumming her fingers on the steering wheel and singing along to her music as it filtered through her car. Whenever she hugged someone she became quite happy as well, leaving a lingering warmth radiating off them as well.

He felt excitement. This was a thrum of electric tension coiled in the chest. A small brunette from across the street became excited every day at four o'clock when Sam was home at Bobby's scrap yard and they were scheduled to train together. She'd joined the force quickly after a werewolf on his way to avenge his dead mate and kill Bobby ran into her on the sidewalk walking home from the grocery store.

Emotions were all simple to learn, individually. The rebel angel encountered a difficulty once he could interpret them, however. Did you know humans are even capable of feeling more than one specific emotion at one time? Castiel certainly hadn't. Sometimes he could feel Dean's emotions intermingling between anger and sadness. Sam usually felt tense- just in general, no emotional heading assaulting his mind- and semi nostalgic. The dark haired angel was almost certain he was remembering the small portion of his life he spent in college. It was the most peaceful time of his life.

When situations became intricate, emotional overlap became overwhelming- especially to the angel who tried so hard to understand his friends in order to be of assistance once the problem has been averted, even just for the mean time. It became... hard, for Cas, to feel emotions such as his friends had shown him and be able to sympathize where even empathy used to lack in his being, but not be able to cure their emotional wounds.

There was only one emotion that Cas had yet to properly understand: The emotion of pain. There were different types and mysterious causes- some created by internal agony and others by external conflict- Cas had begun to get confused as to which he was facing. He understood emotional weariness. He understood the pain of lonliness. He understood the pain of physical injury.

Yet none of those compared to that of grief.

Grief was a barrelling onslaught of pain. Physically, it created the illusion of a tightened heart and throat. Blood and pulse raced faster. Breaths came harsher.

Emotionally, burning waves of release exited the human soul as it cringed into the darkest recesses it could find to protect itself, effectively snuffing out the energy's flame as well, causing a coldness the angel could only imagine in the pit of a human's stomach.

Mentally, denial and confusion intermingled to cloud all concious thought, furthering the heightened power of pain as all that could be registered.

Cas had empathized and spoken of mourning. He had conducted ceremonies for fallen brothers a multitude of times before. Yet, Castiel had never known grief like the small girl had radiated, clutching to Gabriel's jacket as she fell to her knees on the cold hardwood floor when Sam and Dean returned from the Elysian Fields Hotel.

The angel flinched.