damn. laziness is back!!

I bet you all runners have the same problem as me at times.. which is laziness!! I have a 2-month marathon schedule but unable to follow it as planned sometimes, such as being sick at the day I planned to run 21km. I thought I could run the day after but retaliated to run again because I was lazy. I am really afraid that I cannot keep up with the schedule and then unable to run a good full marathon at September (2 months later). Could anyone of you share with me about your running schedule and challenges you faced back then? I am really confused.. whether is my body telling me that I am too weak to run or that I am just being pure lazy.. Oh my, I need some help here!! Btw, I run trails every week and with new balance minimus (closer-to-barefoot shoe).. What about you?