I thought this only happened in books

Some chess books about tactics have puzzles for you to figure out.  Most of them are neat, but you never see them in your games, so you wonder if studying them is even worth the effort.  IT IS!  But they don't just appear. You have to:
1) Know the tactic
2) See the makings of it in your current position
3) Set it up to work

Here is an example of the Greek Gift (Bxh2+ or Bxh7+) sac:

The next uses the same idea, but it needs a little extra preparation, since there is a bishop waiting to take the knight.  But White makes it work anyway:

                           So I guess going through all those books with tactical quizzes wasn't a waste of time after all!  As a matter of fact, improving your tactical ability gives you the most "bang-for-your-study buck" when it comes down to winning games.  Anyone rated below 2200 can always benefit from studying tactics.  They are like tools in your chess toolbox.