Rest is incredibly important in the days leading up to the marathon. Try and relax as much as you can the day before, as well as getting some early nights if you can fit them in. If you're traveling to the event and have spent long hours in a car or a plane, some gentle movement such as a short walk or run, or a light massage (if you're used to getting them during your training) to warm up your muscles can be very beneficial. This can also help calm pre-race nerves, help you sleep better on the night, and loosen up your muscles before the hard day ahead. The important thing is to be flexible and listen to what your body is telling you it needs - whatever is going to make you feel fresh and ready on Sunday morning is the right thing to be doing.
Daydream for success
The night before the marathon, it's very common for pre-race jitters to keep you up long after you should have been asleep. Use the time wisely by closing your eyes and visualising yourself running the race feeling strong, with a smile on your face, and crossing the finish line to a new personal best. This will help get you into a positive mindset for the task ahead, and the pleasant thoughts will help you drift off more easily than if you spent that time worrying about what could go wrong.
If sleep is an issue, try a guided meditation, or deep breathing exercises - take a deep breath in through your nose, counting to six and slowly allowing your diaphragm to expand. Then slowly breathe out through your mouth, counting to seven and allowing your breath to completely leave your chest. Pause a few seconds and repeat about 10 times, or until you feel tired enough to fall asleep naturally.
Now is not the time to try something new
Those cool looking new energy gels your friend is raving about? That new sports bra or pair of running shoes you treated yourself to but haven't gotten round to wearing yet? Now is not the time to turn yourself into a human guinea pig, so stay away from anything that isn't already tried and tested on your long runs. The last thing you want is a nasty blister, or a bad case of 'runners tummy' when you're halfway around the course.
It takes time to go from dehydrated to hydrated, so think of consuming water regularly in the days leading up to the race. The International Marathon Medical Directors Association has suggested that marathon runners drink about 400-800ml of fluid per hour, with the upper level being in warmer environments for faster and heavier runners, and the lower level in cooler conditions for slower runners. If in doubt, check your urine - a dark colour means it's time to up your fluid intake. It's important not to drink too much at once though, as this can lead to a nasty condition known as hyponatraemia, which causes your cells to swell from lack of sodium, and can lead to vomiting, headaches, or seizures. Not fun! Sports drinks can be helpful to ensure that you're getting a good supply of sodium as well as carbs along with your fluid, but make sure that you're used to whichever brand you go for on the day, to prevent any finicky stomachs.
Try and make a habit of drinking water in the days leading up to the race - keep a two litre bottle near your desk or anywhere else that you spend a few hours at a time, and sip it regularly throughout the day. If you find plain water boring, try sparkling, or adding a little lemon juice or other flavouring to encourage you to drink more.
Plan your breakfast
They say breakfast is the most important meal of the day, and this is definitely true on the morning of a marathon. Plan what you're going to be eating ahead of time, and make sure you have it to hand. This is especially important if you're in a hotel the night before - don't assume that they'll be able to whip you up your favourite pre-race breakfast when you need it. A marathon is tough enough without having to do it on an empty stomach, or one that hasn't had enough time to digest the food that's in it.
Try and eat a good, carb rich meal 2-3 hours before the race, in order to replenish your glycogen stores, which will be the fuel that you'll be running off during the race. Some good options include a bagel with peanut butter, toast with honey, or oatmeal with banana. Make sure whatever you eat is something that you've had before long runs in the past, and that you and your digestive system is familiar with.
Figure out exactly what you need to pack, the logistics of where you're going to be leaving your baggage, and detailed directions of where you need to be, as well as how long it will take you to get there. Always leave longer than you think you'll need to set off - the last thing you want is a frantic dash to get there because there wasn't a parking spot within a mile of the starting line.
Lay our your clothing the night before, to avoid any: "Oh no, I left my running shoes at the gym!" panics. Set two alarms - this will ensure that you get up when you need to be, as well as helping your peace of mind, which will help with getting a good nights sleep.
There's no such thing as bad weather, only bad clothing
You can't control the weather, but you can be prepared for whatever Mother Nature throws at you. Check it the day before and plan your wardrobe accordingly. Cool weather may call for a hat and gloves, whereas a windbreaker may be required in gusty weather. Wear light clothing with good coverage if the sun is meant to be shining, and don't forget the shades and sunblock!