I know the difficulty with "concentration" and making your mind still while meditating.  I found that any background music with lutes, harps and bells is helpful for me.  I particularly enjoy a CD called "Mozart Naturally".  It helps calm me at any time of the day or night.  I found that I do not have trouble with guided meditation, but if I am on my own, sometimes I have to focus on a flickering candle flame to still my racing thoughts.