Energy is all around us, and it takes many forms; from the energy within ourselves, to the energy in each living entity, or non-living (some things are debatable). Some people have a short supply of personal energy, and need to feed from others or from the energy that surrounds us in the environment...we call these people vampires, for there is no other term available. Without feeding, they become weak, some ill, but is it truly a condition of poor energy, a mental imperfection, or a true medical problem?
Then there are therians, whose souls are melded with an animal, and are a store house of energy due to two entities being bonded together. It is not unusual for therians to be empaths, healers, even shamans/ess' because the extra energy they have can be given freely. If they give too much of themselves, their energy can run low, but their methods of getting a "pick me up" of energy could be from just getting a good sleep, to eating a terrific steak.
Spiritual energy, or that derived from deities, is a more sublime form of energy, and usually comes to us when needed; during hard times, rituals and spellworkings, etc. But while most of the energy comes from within ourselves, the energy given by deities is deemed a blessing...a spiritual boost.
Negative energy, that which is used for "bad" intentions; but what does "bad" really constitute? If someone believing in "all is light, all is good" feels that someone needs to "see the light", and works a spell upon them to influence their thinking...is this good energy being sent out because the spellworker's intentions are, what they feel, good. Or would you say this is negative energy being sent out because they are trying to influence someone without the person's knowledge or consent?
Energy cannot be created nor destroyed, just reshapened. In essence, how we use energy, and send it out, would fall inside how we define good/bad, good/evil, black/white when it comes to magick. Intentions, not only how we perceive it, but how others perceive it.
Someone casting a spell could have good intentions, but it is perceived as bad by someone else. So the person casting the spell believes they are using and emanating positive energy, while the other person believes the energy is negative.
This will always be debatable, for each individual enjoys the freedom of having and knowing their own intentions; and they don't "have to" understand anyone else's, especially when they "know" they are in the right.