Sometimes easier said than done but try not to let it stress you out! Fitting a training schedule into an already busy life is very challenging- but it is totally doable and you have made a choice to do it. If you feel yourself getting stressed about it then try and remember why you're doing this- i.e.(hopefully) you love running and want a challenge. Also try and keep things in perspective- missing an occasional session is not the end of the world I promise!
Don't just run- this is also easier said than done and to date I've been my own worst enemy. But do some strength training, and do some yoga (this YouTube video is my favourite)
In my experience training for a marathon is harder than running the actual marathon- enjoy race day and soak up the atmosphere and memories!