Full Idea
For Nietzsche, the true belief is the one which augments one's power.
Gist of Idea
True beliefs are those which augment one's power
Source
report of Friedrich Nietzsche (The Will to Power (notebooks) [1888]) by Roger Scruton - Short History of Modern Philosophy Ch.13
Book Reference
Scruton,Roger: 'A Short History of Modern Philosophy' [ARK 1985], p.193
A Reaction
Sounds suspiciously like pragmatism. Sounds suspiciously unlike truth as we know it. So many philosophers seem to me to confuse the concept of the truth itself with the ability of humans grasp the truth, or be interested in it. Truth is not part of us.