Can extensive creating, copying and erasing files eventually ruin a HDD? The HDD of my Early 2011 MBP broke, and I'm considering if it's because of the heavy workload I put it through by installing, deleting, downloading, copying and erasing files, over and over. 
I thought about it, and logically it would make sense that this would eventually wear down a HDD, but since I'm not an expert, I was wondering if I was right in this assumption, or if I was just unlucky with my HDD?

Also, I'm using my new computer now, and I'm worried the same might happen to it eventually, if I don't take preventative measures early on.
Everything eventually wears out, it's just a matter of time and a fact of life.  Since it's an unknown as to explicitly why your HDD failed it can only be said that normal/excessive usage leads to normal/excessive wear and tear which does contribute to the eventual failure.  The only thing you can do about it is to ensure that you always maintain proper and current backups so in the event it fails you do not loose important files.