The success of most things depends upon knowing [well] how much time is needed to succeed.

[Les succès de la plupart des choses dépend de savoir combien il faut de temps pour réussir.]

Charles-Lewis de Secondat, Baron de Montesquieu (1689-1755) French political philosopher

Pensées Diverses [Assorted Thoughts], # 1007 “General Maxims of Politics,” No. 15 (1720-1755) [tr. Clark (2012)]
    (Source)

(Source (French)). Other translations:

In most things success depends on knowing how long it takes to succeed.
[E.g. (1874)]

Success in most things depends on knowing how long it takes to succeed.
[E.g. (1883)]

The success of most things depends upon knowing how long it will take to succeed.
[E.g. (1915)]

Success in the majority of circumstances depends on knowing how long it takes to succeed.
[E.g.]

Success generally depends upon knowing how long it takes to succeed.
[E.g.]