Upon finishing the Marathon after a time of 5 hours and 10 minutes or so I remember distinctly feeling very stiff, and altogether in pain. My right foot was in pain around the middle, I could feel a blister somewhere on my left foot, and my muscles in my legs were all together seized up. I staggered a little bit but managed to keep my balance as I drank some water, gatorade, and snack on a banana.
A good tip to remember is KEEP MOVING. Don’t stop walking around so as to help get your muscles relaxed, and be sure to fuel up slowly on snacks like trail mix, granola bars, nutritional snacks cause I bet your stomach is going to be super hungry. I know mine was! Try doing a little stretching as well like bending down and touching your toes or lifting up your legs and stretching them back.
I can guarantee you that it will be hard to walk around for a bit, not to mention sitting down. Last but not least, try getting a good rest-in. ZZzzz