"It's liquid luck. It makes you lucky!"
Felix Felicis, also called "Liquid Luck", is a magical potion that makes the drinker lucky for a period of time, during which everything they attempt will be successful.
It is meant to be used sparingly, however, as it causes giddiness, recklessness, and dangerous overconfidence if taken in excess. Felix is highly toxic in large quantities and is also a banned substance in all organised competitions, such as Quidditch, along with all other methods of cheating. It is very difficult to make, disastrous if made wrong, and requires six months to stew before it is ready to be consumed.
I loved the idea of this potion, but I also loved all of the connotations which came with it. I loved that Rowling created these negative sides to it as well to show the dangers of the existence of such things. Sometimes though, everyone needs a little 'liquid luck'! How about you guys?