In Eph. 4:15, the Apostle Paul calls us to "speak the truth in love." The following may serve as illustration.
Imagine a train crossing a bridge over a deep chasm. The train is truth; the bridge is love. In relationships with others, we must first build up our love for them, and their perception of it. Only then may we send the heavy truth of truth between us.
So, when you are faced with a potentially difficult conversation, always ask yourself: Is my relationship with this person rooted firmly enough in love to bear the weight of the truth I wish to communicate? Our goal is to "speak the truth" for the maturity of the Body (Eph. 4 context). But what good will it do to speak the truth if the train crashes in the chasm?
(revised from a note of my father's)