Full Idea
Clearly it is often the part of wisdom to believe what one desires; for the belief is one of indispensable preliminary conditions of the realisation of its object.
Gist of Idea
It is wisdom to believe what you desire, because belief is needed to achieve it
Source
William James (The Sentiment of Rationality [1882], p.43)
A Reaction
Roughly, action is impossible without optimism about possible success. This may count as instinct, rather than 'wisdom'.
Book Reference
James,William: 'Selected Writings of William James', ed/tr. Bird,Graham [Everyman 1995], p.43