Each of us has the need to pray; it is an expression of the soul,which yearns–with or without our conscious recognition–to turn to the holy.
In some people, this need is so clear and strong that their problem is not how to find time for prayer but how to constrict prayer within the time allotted to it.
Others must rely on the formal prayer schedule in order to pray at all.
We can compare the need to pray with the feeling of hunger–which is a deeper analogy to prayer than may be initially supposed.
Although we have an instinctive need to eat, we subject that need to a schedule.
Sometimes a person eats not because he is hungry but because mealtime has arrived.
So, every individual has an inner need to pray, to pour out his heart in the worship of God.
However, that need is not necessarily synchronized with the formal prayer services.
–Rabbi Adin Steinsaltz
From "Prayer" in The Thirteen Petalled Rose (new edition) by Rabbi Adin Steinsaltz