Is it possible to run too many training kilometres?

Kathleen asks

Hi Lee,
I've recently signed up on Marathon Guru to help me achieve completing my first marathon (Gold Coast) For the last three years I’ve been running approximately 14km daily (+ one longer run ranging between 18-24km) and having one rest day per week. In that time I’ve done lots of fun runs including a few +18km runs and two half marathons. My best time was 1hr 40mins and I pulled up pretty sore!  I'm a creature of habit and I'm finding it difficult to reduce my km and stick to the program (Ie: todays easy run- 6km at 6.22 pace). Am I being too eager? Should I reduce my km and stick to it? Excited to try the varying sessions yet feel like in going slightly backwards. Am I starting in the right program? Started working towards this over a year ago.
This venture is completely unknown to me and I’m probably being silly.  
Love the interaction your site provides and thanks for having such a great interactive resource. I mostly train alone and I appreciate any advice.
Many Thanks,
Kathleen :)

Lee's response

Hi Kathleen,
I know the program feels very easy at the moment and like you are taking a step backwards and this is true in one aspect as you are doing less mileage BUT you will be doing quality sessions that you have never done before and this will have an affect on your body that if we combined more mileage at this early stage, you will probably break down.
The objective for us is to take individuals like yourself that have not really done a structured training program with long runs, medium runs, easy runs and quality sessions before and start out easy and each week build you up. The first few weeks are introductory weeks and then the training picks up through to week 12 before starting to freshen up the last month before your marathon.
You will find the easy runs very easy but lets see how you are feeling after the first 4 - 6 weeks when you are doing your long runs on tired legs from the continual training each week + the quality sessions which your body won't have been used too.
I hope this eases your mind a bit and look forward to chatting further once you are really into the training block. Enjoy the early days as we still have 13 weeks to go.