A "psivampire" is merely a person who needs or feels the need to draw energy from his or her surroundings, and the living things within them. Many of these people are characterized by the distinct decline in energy, mood, and in some cases, aspects of health if they are cut off from outside energy supplies for an extended period of time. This is generally credited to a lack of or inability to retain their own energy in a reasonable and healthy manner. It should be heavily noted that literally any person who can sense and control energy has the ability to draw it from their surroundings, and it is in-fact a common practice among spell casters of many paths. The only significant difference between a "psivampire" a regular person is the aforementioned declines. Anyone can be a vampire unto their surroundings in many forms, and it isn't in any way special, different, or
glamorous. Some people are born with an energy deficiency, but it can be healed or countered with other magick.
I'd also like to point out;by you learning to take energy from your surroundings, it won't make you a psychic vampire, it will simple be you learning a rather basic skills.