Talk with God with the thoughts that your heart is full of. If you enjoy the presence of God, if you feel drawn to love him, tell him so. Such conscious fervor will make the time of prayer fly without exhausting you, for all you will have to do is to pour forth from your abundance and say what you feel.
But what, you ask, are you to do in times of dryness, inner resistance, and coldness? Do just the same thing. Say equally what is in your heart. Tell God that you no longer feel any love for him, that everything is a terrible blank to you, that he wearies you, that his presence does not even move you, that you long to leave him for the most trifling activity, and that you will not feel happy till you have left him and can turn to thinking about yourself. Tell him all the evil you know about yourself.
So how can we even ask what there is to talk to God about? The pity is that there is only too much... In this way, either God’s mercies or your own miseries will always give you enough to talk to him about. The subject will never be exhausted!
In either of these two states I have described, tell him without hesitation everything that comes into your head, with the simplicity and familiarity of a little child sitting on its mother’s knee.