I think there is a difference between using something as an excuse, and being realistic. It is realistic to acknowledge ones' deficits, but an excuse if you let them hold you back from doing things that you are good at. I think confidence and self-esteem play a major role as well, in how effectively you live your life.
Like my psychologist said to me a while ago "Productivity is in the eye of the beholder. Do not measure your productivity against societies norms. In areas where you are very productive, others may not be. It is all relative." I often chastise myself for procrastinating, delaying and being indecsisive, but as I get older, I realise that it is my FUNCTION to be this way. That if I do things before I am ready, it results in failure for me. I may have pleased someone else by my lightening effiency, but I pay the price, usually with a long period of shutdown and an increased amount of rocking in front of my fridge staring vacantly in to space as my poor brain recovers. And I get no thanks for destroying myself, to make someone else's life easier.
Do not beat yourself up. Your process takes the time that it needs, others will just have to accomodate, or sign up for active service and leave the country.
Mics