I have never been a high energy person but the older I get the harder I find it is to concerntrate. And sleep is the very best form of escape. Some days are better than others.
My suggestion would be to set small goals each day...baby steps. Also, think about your caffeine intake and sleep patterns. I am at my worst when I don't sleep well and can't catch a nap (for whatever reason). Also, I am better when I don't have the TV on (ie DH is not up yet or has already gone to bed). Music helps, especially lively music.