Praise and criticism are not opposites; in many ways, they are very similar. Both are primarily forms of attention, and are most effective when specific rather than generic. Both should be deployed with concrete goals in mind. Both can be diluted by inflation: praise too much or too often and you will devalue your praise; the same is true for criticism, though in practice, criticism is usually reactive and therefore a bit more resistant to devaluation.
— Karl Fogel, Producing Open Source Software
Wounds from a friend can be trusted, but an enemy multiplies kisses.