Concentration

For years I have been in school now. I know I am smart and a good student, but I have a little problem with concentration. In the past I had an accommodation that would help me with this, but since I only returned for one quarter I didn't bother; I really regret that now. I sit down all ready to work and then I just can't get it out. I am behind in my work and I understand that I have been through a lot this spring quarter, but I was hoping for so much better. I guess the point is that I am not giving up. I just need to find a way to stop being so hard on myself and accept that I did the best I can.