When you run a marathon there are two main aspects that can have a great bearing on the performance - the training you have done leading into the race, and secondly the mental aspect of the race. If you have done all the training you have set out to do in the months before the race, and you are on the start line with no injuries, then you are half way there to having a great race. There is no reason you should be thinking negatively as there is nothing more you could have done up until this point.
The race start
When the race starts you want to be relaxed and comfortable for the first few miles, there is no need to push the first couple of miles and start panicking that you are not on your set pace. The last thing you want to be thinking is how far there is left to run. Getting to 2 miles and thinking to yourself "There are 24 miles to go!!" is not going to help you.
You need to break the race up in your head and tick these off as you go. What some athletes do is break the race up into 4 x 10km (then a little 2km sprint at the end!). This is effectively a quarter of the race and is much easier to get your head round than the whole race distance.
When the going gets tough
You are going to go through at least one bad patch in the race, perhaps even a couple. There is no way round this, you just need to deal with it when it comes and know that it will not last long. If you have done the training then you know physically you can handle the marathon and you need to focus on riding out the bad patch.
During a bad phase it might be an idea to set smaller targets, for example breaking the race up into 1km intervals.
During a bad phase it might be an idea to set smaller targets, for example breaking the race up into 1km intervals. Get to the next 1km and then the next, and so on. This will keep you focused on the distance and you should hopefully maintain your pace. This will allow you to focus on something else rather than how you are feeling. Just keep thinking positive thoughts and think of all the training you have done to get you to this point. You don't want doubt setting in, you CAN do this, you WILL run well.
Don’t worry if your mind starts to wander
You are not going to be able to focus for the whole race, your mind will start wandering during the race and this is ok, providing you don't wander for too long! Take in some of the sights on the course, but slowly get back to focusing on the race and getting to the next checkpoint in your head. Don't be put off by runners going past you, you need to run your own race and not focus on anyone else - unless of course they are your own personal pace maker.
Don't be put off by runners going past you, you need to run your own race and not focus on anyone else.
It is a good idea to know the last couple of miles of the route beforehand, doing an easy jog over the last couple of miles miles the day before the race will help when it comes to the race. You'll get to that point in the race and it will feel familiar and you'll know exactly what the course looks like from that point on and they'll be no hidden surprises, like a massive hill!
As I said at the start, half the battle of the marathon is getting to the start line in one piece having had a solid build up in training not full of disruptions. If you can do that, all you have to do is put into practice what you have been doing in training. Don't think of it as a race, think of it as a training run with thousands of other people!