Felix Felicis

Felix Felicis (Fee-LICKS Fi-li-siss) is the name of a
fictional potion in the book Harry Potter and the
Half-Blood Prince that grants temporary good luck to the
drinker. The name, like many things in the Harry
Potter novels, is Latinate in origin, and translates to
"lucky of lucky," or "happy of happy." ("happy", strictly speaking,
means "lucky.")

A chapter of Half-Blood Prince is titled "Felix Felicis,"
and this was one of three chapter titles revealed prior to the
book's release; this was possibly done as a kind of red herring, as many people were
suspecting it to refer to a character, as "Felix" can also be used
as a name.

Spoiler warning: Plot and/or
ending details follow.

The Potion

The potion is supposedly extremely difficult to brew, requiring
six months of preparation and time to stew properly. In addition,
it can all too easily fail, resulting in a potion with dangerous
consequences.

The potion looks like molten gold, and when it is put to boil,
drops of the potion fly upward, but not a single drop is
spilled.

Having too much of the potion is like having "too much of a good
thing," and the drinker experiences, as Professor Slughorn describes, "giddiness,
recklessness, and dangerous overconfidence."

Felix Felicis is also banned from all competitive events i.e.
elections, sports etc.

The potion's means coincide with Rowling's own personal
philosophy. When asked on her website whether or not she believes
in fate, Rowling responded, "No, I believe in hard work and luck,
and that the first often leads to the second." Rowling feels that Felix best exemplifies this
philosophy, as it is the user's confidence in himself that leads to
his being "lucky."

Half-Blood Prince

In the novel Harry Potter and the
Half-Blood Prince, Potions professor Horace Slughorn has brewed a cauldron and
offers a small bottle, good for twelve hours of luck, to the winner
of an in-class Potions-brewing contest. Harry
Potter wins the contest with help from the notes in his
textbook, that is supposed to have belonged to the Half-Blood
Prince previously.

Harry pretends to spike his friend Ron
Weasley's cup with the potion before a Quidditch match,
resulting in confident playing from Ron, who believes himself to be
lucky. (A prime example of the placebo effect, this is also much like the use
of the "Magic Feather" in Dumbo.) Harry is tempted not to use the
potion because he has hopes for it that show some of his true
colors when it comes to Ginny. He secretly hopes to use it to have
Dean and her break up and daydreams that they will then get
together. Harry uses up a quarter of the Felix Felicis to persuade
Professor Slughorn to give him the memory that he had tampered
with, inadvertently breaking Ginny
Weasley (his secret crush) up with her boyfriend, Dean Thomas, and
also his best friend Ron Weasley up with his girlfriend Lavender Brown (whom
he had gotten very tired of).

Before departing with Albus Dumbledore to find a Horcrux, Harry
gives the remainder to Ginny Weasley, Ron Weasley and Hermione Granger in order to give them luck
when facing Draco Malfoy's scheme. This proves to be
fortunate in itself, as they manage to confront several Death
Eaters but are not seriously hurt. Afterwards, they directly
attribute their survival to the potion.

It seems apparent that Felix Felicis can make your hopes for the
potion work in a very small amount of time. For instance, Harry has
the inclination to use the potion to get Ginny to fall for him and
Ron to break up with Lavender, however when he drank the potion he
was concentrating on getting the memory from Professor Slughorn. In
a matter of a few minutes, by becoming invisible and letting
Lavender see only Ron and Hermione coming down from the boys
dormitory and brushing between Ginny and Dean, making Ginny think
that Dean had helped her to get through the portrait hole, a habit
which she finds annoying, Harry has achieved two of his goals while
on the way to getting the third.