Luck or fortuity is good fortune which occurs beyond one's control, without regard to one's will
Will (philosophy)
Will, in philosophical discussions, consonant with a common English usage, refers to a property of the mind, and an attribute of acts intentionally performed. Actions made according to a person's will are called "willing" or "voluntary" and sometimes pejoratively "willful"...

, intention
Intention is an agent's specific purpose in performing an action or series of actions, the end or goal that is aimed at. Outcomes that are unanticipated or unforeseen are known as unintended consequences....

, or desire
Desire (philosophy)
In philosophy, desire has been identified as a philosophical problem since Antiquity. In Plato's The Republic, Socrates argues that individual desires must be postponed in the name of the higher ideal....

d result. There are at least two senses people usually mean when they use the term, the prescriptive sense and the descriptive sense. In the prescriptive sense, luck is the supernatural
The supernatural or is that which is not subject to the laws of nature, or more figuratively, that which is said to exist above and beyond nature...

 and deterministic
Determinism is the general philosophical thesis that states that for everything that happens there are conditions such that, given them, nothing else could happen. There are many versions of this thesis. Each of them rests upon various alleged connections, and interdependencies of things and...

 concept that there is a force which prescribes that certain events occur very much the way the laws of physics will prescribe that certain events occur.

Luck is the residue of design.

Branch Rickey|Branch Rickey, as quoted in Psychology Applied to Work : An Introduction to Industrial and Organizational Psychology (1982) by Paul M. Muchinsky, p.482; this has often become paraphrased as : "Luck is the residue of hard work and design."

Fortune turns all things to the advantage of those on whom she smiles.

François de La Rochefoucauld, Maxim No. 60, Reflections; or Sentences and Moral Maxims (1678)

Luck can only get you so far.

J. K. Rowling|J. K. Rowling, Harry Potter and the Half-Blood Prince, Hermione Granger|Hermione Granger referring to a luck potion Felix Felicis

We are all vainer of our luck than of our merits.

Nero Wolfe in Nero WolfeThe Rubber Band|The Rubber Band (1936) by Rex Stout

Fortis fortuna adiuvat Fortune favours the brave.

Terence (195-159 BC), Phormio, 203; variant translation: Fortune favors the bold.

The only thing I ever learned was that some people are lucky and other people aren't and not even a graduate of the Harvard Business School can say why.

Kurt Vonnegut, as quoted in "The Sirens of Titan" by character Noel Constant