The Week Before The Marathon...
You have aches and pains
Time for some honesty here. Are your muscles just feeling tight in which case, get a proper massage or do you have an unresolved injury? If its the latter, particularly if it has been severe enough to affect your running in the last week, bite the bullet and hold your marathon entry over to next year.
You get ill
If you have flu or any illness other than a light head cold, you should defer your entry until next year. The same goes if youre taking antibiotics or if youve discovered that youre pregnant. If you think you have a temperature on or close to race day, check that its not just nervous sweatiness. If a thermometer reveals that you do have a temperature, dont race.
Youre not sure which target to aim for
You may have been training better than you expected recently, or conversely consistently missed the time targets for the build-up races in your schedules. Revise your goal using the guidelines printed at the top of your schedules, and aim for a conservative first half that will allow you to assess your fitness halfway round the marathon and speed up or slow down from there. As a rough guide, do the first half 10-15 minutes slower than your best recent half-marathon time (or the first 10km five minutes slower than your recent 10K race time). If you havent raced recently, consider using your heart rate as a guide, aiming for around 65-75 per cent of your working heart rate.
Youre restless and full of energy
Thats natural in these easy weeks, partly because youre used to hard training and partly because we find it hard to passively await race-day. But fight the temptation to train more even cross-training and dont take to DIY or gardening to keep your body occupied.
You have put on weight
As you reduce your training but (hopefully) continue to eat the same as before, your body will fill your muscles fuel reserves with glycogen. It will also store essential water with it. This is vital for race day, and far outweighs the inevitable slight weight gain.
People are still telling you you cant do it You can.