People often say ‘I have no idea why I did that’ as if it’s an excuse. As if according to the laws of our universe of increasing entropy and prior causes, such a thing as an ‘excuse’ could possibly have any meaning anyway. Really, no one could possibly know exactly why they do anything…one simply feels a certain inclination which they act upon and then invent or partially relate a ‘reason’ for it after the fact. A person saying ‘I have no idea why I did that’, simply hasn’t been able to find an adequate and rational-sounding fabricated cause for their action. It is in this sense that none of us knows why we do anything. No one can explain to you or to themselves why you are the way that you are, or why they are the way that they are. It is just so. If such a notion fails to bring you comfort, take comfort in the simpler explanation, which is that everything any of us do is for the exact same reason: an intricate steam of prior causes stretching back to the Big Bang. To feel ‘I don’t know why I did that’ is simply to temporarily lose your false ongoing sense of free-will. If you step back you will realize that this will necessarily be your answer to any and all questions regarding your actions.