There are often times in our lives when we sit down to pray and feel nothing. We don't experience any joy or peace, and we struggle to pray.
We may even be tempted to give up on prayer.
St. Francis de Sales recognizes this situation and wrote a letter to St. Jane Frances de Chantal, who was experiencing such spiritual dryness.
This advice may not seem very consoling, but it is very honest, recognizing that such a trial is to be endured with the grace of God, challenging us to use our will to remain faithful to God.
St. Francis de Sales continues his letter, challenging Madame de Chantal to offer these sufferings to God.
If you experience dryness in prayer, don't give up, for Jesus is calling you closer to himself, challenging you to give-up the "sensations" of prayer and to prove your love of him in every circumstance.
This is what the saints did in their lives, loving God when all joy and peace in prayer has been removed.