It was my very great privilege to hear Henri Nouwen give a series of lectures at Virginia Theological Seminary in the 1970s. Here's something he said about prayer:
To pray, I think, does not mean to think about God in contrast to thinking about other things, or to spend time with God instead of spending time with other people. Rather, it means to think and live in the presence of God. As soon as we begin to divide our thoughts about God and thoughts about people and events, we remove God from our daily life and put him into a pious little niche where we can think pious thoughts and experience pious feelings. ... Although it is important and even indispensable for the spiritual life to set apart time for God and God alone, prayer can only become unceasing prayer when all our thoughts -- beautiful or ugly, high or low, proud or shameful, sorrowful or joyful -- can be thought in the presence of God. ... Thus, converting our unceasing thinking into unceasing prayer moves us from a self-centred monologue to a God-centred dialogue.
-- Henri Nouwen