How you feel and how strongly you feel while casting is what powers your magick. If you wish predict the potency of a spell, converse with yourself and how strongly you feel will tell you exactly how powerful the magick was. Say your emotions are murky and mixed up, it would be like filling you car up with watered down gasoline; it's not going to get you as far, and if not, nowhere at all. Yes one should separate disconnected emotions and enter what some would call a trance-like state while casting, but your magick is only as powerful as the energy you put behind it, so for the love of whatever you warship, put something behind it. Oh and just a disclaimer- i'm going to use a metaphor to describe this disclaimer. Magic is like getting into a fight, you don't need a reason to get into it, but it helps decide how your going to fight. The emotion driving your magick is like the rage driving a punch. If you let your rage get out of hand, it'll be easy for you to miss your target. That's where the candles and herbs come in. They're there to make you think and calculate where your punch is going to land and how your target is going to react. Everyone has their own fighting style so all have a different balance of emotion and thought. It is effective to be very strong, but without dexterity and planing, strength and size can lead to one's demise. Conversely, A complete lack of emotions and fantastic battle tactic and skill will lead to a lot of easy victories, but takes extended periods of training.
So what I'm trying to say is take the time to decide what balance of strength and dexterity will be required to defeat your opposition, because everyone fights differently.
To each his own, and this is mine. Please disclaim me, for I am young and ignorant, barely scraping at a hope of understanding. Just please tell me why I'm wrong if I am.