Ten, maybe even five years ago I probably couldn't give you a clear definition of what a sadist was. But I've gotten my kicks from seeing other people suffer for as long as I can remember.
My earliest recollection of my sadistic tendencies extends to when I was probably only three or four years old. My baby sister was two years younger than me. I decided to pee into a cup and present to her as lemonade. The details of the incident are hazy, but I think she ended up drinking some of it and I enjoyed quite a chuckle.
Another early memory stands out in my mind: In kindergarten, when I was six years old, I had a female friend that I had known from carpool trips to preschool. In the classroom, right next to the door, there were little shelves with everyone's name on them that the teacher used to pass paperwork back to us. The name tags were made out of construction paper and were simply taped on. Early in the school year, I was hell bent on tearing my friend's name tag in two when I came into the classroom in the morning. As soon as the teacher put a new tag on, I would rip it again. This went on for three or four times until the teacher made a point to ask the whole class who kept on ripping my friend's name tag. There was complete silence in the room, and I dared not even look at the teacher (probably a dead give away). Nonetheless, I reasoned that the blame would shift away from me if I continued to rip the name tag. (After all, I thought, who in the classroom would dare rip it again after that stern talking-to?). My efforts were finally thwarted when the teacher covered the whole name tag in tape, making it impossible to tear. I never did get caught--at least I never got disciplined or yelled at--but I'm sure the teacher knew it was me. I certainly derived great joy in causing my friend that series of tiny hardships.
I once read that Internet trolls practice their trade because they want to bring everyone else down to their own level of inner misery. From experience, that sounds right to me; until recently I was an avid troll on sites like Slashdot. I would add that in addition to wanting to make people feel miserable (or at least annoyed), trolling for me was the only natural way to "socialize". I have never been able to carry on friendly dialog in Internet forums or instant messenger chats, especially not with strangers. The whole social networking craze scares me. But I have fantasized about having unlimited destructive power in games like SecondLife. I have spent a great deal of energy trying (mostly unsuccessfully) to subvert Slashdot's abuse filtering system.
I now understand that my sadistic nature (along with a whole lot of other issues, which I will get into over time) is a great impediment to my goal of achieving healthy relationships. Right now I am in the stages of fighting off my impulses, but I suspect they are deeply ingrained in my psyche. Only time will tell if I am successful. I realize that I am in for a lot of work, with failures and setbacks along the way.