First remove the myth from your mind that meditation is concentration, focus, and silence. Meditation is your resolve to sit and watch your monkey mind in action, non-judgmentally, watching and accepting the mind as it is and not as you expect it to be. Eventually, your monkey mind will transform itself in the light of your awareness into Buddha-mind.
Meditation is observation, mindfulness, awareness, period.
Let not meditation become another area of stress in life!! Yes, when you are not able to concentrate you feel frustrated, and start impregnating your subjective mind with “This is not for me!” Meditation is not concentration, it is relaxation and letting go. When you relax your body muscles and your brain muscles something happens, that is meditation, beyond definition. What follows out of it is the Meditative state of pristine mind. That is who You are!