Think of it like a more violent version of dreamotion: Emotions can have a strong influence on magic in general given magic -- when you get down to the nitty gritty -- is controlled via will. Strong emotion can heighten one's willpower like determination or anger or weaken it like fear.
Blood is vital to one's survival and comes the closest physically to the core of one's existence and vitality, the soul. It's raw energy in its purest form at that point which makes it an incredibly potent ingredient. As the owner of that blood grows older and begins mixing with others on a more carnal level, powerful emotions to, as the old saying goes, "get one's blood up" can make up the gaps in power when compared to more barbaric practices such as sacrificing newborns who are completely untainted.
It's also the source of many different beliefs surrounding the potency and desirability of virgin's blood in regards to magical creatures.
no subject
Blood is vital to one's survival and comes the closest physically to the core of one's existence and vitality, the soul. It's raw energy in its purest form at that point which makes it an incredibly potent ingredient. As the owner of that blood grows older and begins mixing with others on a more carnal level, powerful emotions to, as the old saying goes, "get one's blood up" can make up the gaps in power when compared to more barbaric practices such as sacrificing newborns who are completely untainted.
It's also the source of many different beliefs surrounding the potency and desirability of virgin's blood in regards to magical creatures.