Emotions

Emotions, also known as humanity, are one of human's greatest weaknesses and strength. Vampires are able to feel emotions more strongly because everything is enhanced. Vampires also have control over their emotions. Emotions are able to empower witches and their magic while werewolves are affected greatly by anger.

Humans
Humans beings are emotional creatures and when they can't control their emotions, it becomes their weakness as it can prevent them from thinking logically or rationally. The basic emotions specific for humans are love (between friends, maternal love or typical lovers' love), grief, anger, joy or surprise.

Witches
Emotions can greatly affect a witch's power, causing it to fluctuate at times. Like werewolves, they can use strong emotions to fuel their magic, strengthening the potency of their spells. Additionally, a witch can subconsciously block themselves through negative emotions namely fear, grief, doubt etc., preventing them from properly practicing witchcraft.

Vampires
Vampires, like humans, are emotional creatures but have the benefit of controlling their emotions by turning them off. Upon their transition the emotions they experience are magnified probably as a means of safeguarding their psyches from the ravages of time, keeping them sane for the extent of their immortal lives. When they want to feel again, they can turn them on or dull their emotions by being in the "middle". A Vampire who has completely turned off their emotions is also said to have completely shut down their humanity, making them carefree and remorseless about their actions and impervious to guilt and conscience turning them into remorseless calculating killers. As a vampire ages, they have less control over their emotions. For example, Rose said she was unable to completely turn off her emotions in By the Light of the Moon. Presumably, like with a Vampire's strength and speed, their emotions intensify with age; reaching a certain age would mean they would lose the ability to shut off their humanity forever. It is mentioned that when a human is turned into a vampire, all of their feelings and emotions are heightened, meaning that pain would turn into agony, sadness into depression, happiness into elation and much more on.

Werewolves
Werewolves are affected greatly by specific emotions, namely anger and rage. While these make them reckless and act irrationally by lashing out, their anger increases their powers. This emotions are felt even by werewolves who have not triggered their gene and felt most intensely on a full moon to the point of going blind with rage.

Werewolf-Vampire Hybrids
Werewolf-Vampire Hybrids experience the same heightened emotions as vampires and initial lack of control, presumably they will act more violent from the effects of anger as felt more intensely from their werewolf side.

Vampire-Witch Hybrids
Vampire-Witch Hybrids experience the same heightened emotions as vampires and initial lack of control, presumably their magic would be more crippled from the effects of fear as felt more intensely from their siphoner side.

Supernatural Hunters
When awakened, a hunter becomes filled with a supernatural urge and hatred toward vampires, this is known as the hunter's instinct. The more vampires a hunter kills, the stronger the urge becomes. This urge is purely subconscious, and forces a hunter to try to kill a vampire even if he or she does not want to. This holds true for both members of the Five and shamanic huntresses created by The Eight Everlastings.

Main Emotions

 * Love - Is the most powerful emotion and strongest affection and personal attachment. Love is also said to be a virtue representing all of human kindness, compassion, and affection "the unselfish loyal and benevolent concern for the good of another".
 * Hope - Is the emotional state which promotes the belief in a positive outcome related to events and circumstances in one's life. Hope is the "feeling that what is wanted can be had or that events will turn out for the best" or the act of "looking forward to something with desire and reasonable confidence" or "feeling that something desired may happen".
 * Friendship - Is a distinctively personal relationship that is grounded in a concern on the part of each friend for the welfare of the other, for the other's sake, and that involves some degree of intimacy. As such, friendship is undoubtedly central to our lives, in part because the special concern we have for our friends must have a place within a broader set of concerns, including moral concerns, and in part because our friends can help shape who we are as persons.
 * Respect - Gives a positive feeling of esteem or deference for a person or other entity (such as a nation or a religion), and also specific actions and conduct representative of that esteem. Respect can be a specific feeling of regard for the actual individual given of the one respected. It can also be conduct in accord with a specific ethic of respect. Despite its positive nature, respect is most often associated with subordination or submission to authority.
 * Fear - Is an emotion induced by a perceived threat that causes beings to move quickly away from the location of the perceived threat, and sometimes hide. It is a basic survival mechanism occurring in response to a specific stimulus, such as pain or the threat of danger. In short, fear is the ability to recognize danger leading to an urge to confront it or flee from it (also known as the fight-or-flight response) but in extreme cases of fear (horror and terror) a freeze or paralysis response is possible.
 * Anger - Is a negative emotion that can is associated with frustration and intimidation. Anger often comes from lack of satisfaction or from a loss of something or someone valuable. It comes from offensive words or actions. Werewolves and Hybrids experience positive affects from anger; anger increases their strength.
 * Hate -  Is a deep and emotional extreme dislike that can be directed against individuals, entities, objects, or ideas. Hatred is often associated with feelings of anger and a disposition towards hostility.
 * Sadness - Is emotional pain associated with, or characterized by feelings of disadvantage, loss, despair, guilt, helplessness and sorrow. These feelings of certain things are usually negative. When one is sad, people often become less outspoken, less energetic, and emotional. Crying is often, but not necessarily, an indication of sadness.

"Humanity switch" users
Below is a list of vampires that have turned off their humanity at least once throughout the book series.