I have often found that if I can't concentrate or I can't maintain a 'good' accelerated state it is because there is often alot of 'other stuff' going on in my life. This situation often seems to present itself when I am trying to relax and fall to sleep. It is as if my mind just hits top gear and can't stop. The best thing I have learnt to deal with this 'mind running' is deal with whatever issue is running through your mind. If I haven't known how to I draw out my ideal outcome and just let it go. My mind seems to sort things out over night and the information that I need to solve my issue just seems to present itself.