Repost from r/marathon-training, thought it might be more helpful here.
Don’t get me wrong I am not a professional runner and marathons are hard. But if you’re thinking of running one, don’t let anyone else put you off. I ran London Marathon in April and it was the first marathon that I’d run. I was genuinely terrified after reading the reviews online around hitting the wall and how hard the last 10k is going to be and how it’s purely pain and I’d really psyched myself up for something awful but if you put the training in and you eat right it is hard but it’s not as bad as what the Internet seems to tell you.
Make sure that you put the training in, consistently, make sure that your carb load properly in the days before, make sure that you’ve got your hydration right and your fuel in right for the day and it will be difficult but you’ll love it. Running a marathon is a real achievement, and I wish I’d read something like this before I ran London.