It's impossible to answer this question without knowing much more about you.
Hard to say based on one line.
Perhaps there is a lack of structure to your day?
Maybe your day is consumed by demands and doesn't include enough time for yourself. It could be that your life is slightly out of balance.
On another level it could be that you have symptoms of depression (such as lack of concentration, low energy, etc).
Fatigue can also be related to a number of physical illnesses.
Nutrition and sleep can affect ones ability to concentrate too.
J