For a long while, I felt very guilty and upset when I found my mind wandering during my prayer session. I think we all have times when our minds just cannot feel the intensity which the Lord deserves during our routine prayer sessions.
I have finally made my peace with these times. I have talked with the Lord many times about this. The mere fact that I give him that time and that I stick it through to the end, tells me that I care enough to devote that time to him. Even if my focus is not as sharp as it usually is, I am offering those moments of time.
On earth, we have many issues to distract us. Spending time with God in prayer, whether joyous or just routinely mild, shows him that I care.
Dear God, I know that you are very aware of what is in my heart; help me to concentrate when I come to you in prayer, and help me to understand that you forgive me for the times when my finite mind wanders from my intention.