No doubt you'll be planning your JMT hike for months in advance. Consider making yourself a "countdown calendar" with notes of important deadlines for reservations and permits. As the day approaches, you'll need to carefully plan your food menus and resupply points. Of all the problems we've heard about from long distance hikers, running out of food is a preventable bummer.
We believe in having a great time, and if you attend to the details in advance you can just hike and enjoy the scenery as your well laid plans unfold before you.