Remember, however, that the Lord never puts a limit or a time guide on our quiet times. The key to overcoming emotional disturbance is the satisfaction of obedience. Successful times with God are not measured by length or depth. They are measured in obedience. We obey by having time with God because He loves us.
Love is the controlling emotion that helps concentration.
A final contribution to loss of concentration is found in the spiritual area. This is the most crucial because it's so subtle. We have a spiritual enemy. Jesus spoke of him and to him as a real person, a real foe. He never attacks in the trivial, only in the crucial.