Full Idea
Weakness of will is misleading, for there is no will, and hence neither a strong will nor a weak one. Multiplicity and disaggregation of the impulses results as 'weak will'; coordination under the dominance of a single one results as 'strong will'.
Gist of Idea
There is no will; weakness of will is splitting of impulses, strong will is coordination under one impulse
Source
Friedrich Nietzsche (Writings from Late Notebooks [1887], 14[219])
Book Reference
Nietzsche,Friedrich: 'Writings from the Late Notebooks', ed/tr. Bittner,Rüdiger [CUP 2003], p.266
A Reaction
That Nietzsche seems to be right is clearer if we remember that the Greek terms are 'control' (enkrateia) and 'lack of control' (akrasia), with no reference to anything called the will.