Why magic works

I've recently been doing some research into more old forms of witchcraft, like how ancient tribes performed it and the kind of objects they used and it made me start wondering. Part of practicing witchcraft is also learning what makes it work and why and I'm really starting to make some great connections. As we do things, often times we don't question why doing them is going to make a difference, but we need to because piecing things together forms a bigger picture and makes everything easier and more understandable.
I was talknig to somebody on a social network and they were saying that dark magic is easier to perform that good magic, and though I don't approve of it necessarily, in a way it does make sense. He said that he would use blood often as an offering to the spirits, which he didn't specify, but he said that he could feel the energy present much faster than if he was donig a ritual without blood, and I think that the reason behind this is because blood is a life force. Everything in our body is manditory in order for us to sustain life, and living we have energy and emotion, but when we're dead we are simply an inanimate object. If you use something that possibly came from a living creature, it's possible that you can manipulate it's lifeforce before it's completely drained out. A lot of ancient forms of magic called for this and if it didn't work then I don't think that they would have continued to perform the rituals that way.
Now please don't get me wrong and think I'm a bad person and I'm gonig to start performnig dark magic, I'm a good witch and I do good magic, but learning about dark magic is also important because it shows a side to witchcraft that good witches like myself haven't experienced. But, back to why I think it is harder for witches who don't practice dark magic to perform rituals succesfully, I think so because we have replaced blood and a lot of parts to a ritual with things like water, salt and other items that never contained a life force so manipulating a force that isn't there isn't possible, so most of the enrgy used comes from ourselves.
Alright, I just wanted to put some more information out there for people to read and gain a better understanding of the craft. I hope somebody somewhere does read this, but if not then I guess that information will just stay with me.