Ugh, this is such a newbie question and I'm embarrassed to ask it. I did a search to see if it's been answered before but didn't find anything.
Every once in a while when I'm drawing and I erase something, it leaves a nasty permanent graphite smudge on my paper that won't go away no matter how much I try to erase it. It's usually not very large but it's enough to ruin the drawing. I make a point of regularly using my erasers on a table or a piece of scrap paper to keep them white and it doesn't seem to help the smudging problem much. Could it be that I erase/draw too hard? Is this a cheap pencil/eraser issue? Or am I just an idiot?