It's always harder to run on the second day because you're still a little sore from the first day. Today was a little hard for me to go on and do a run because of that. However, I was able to push on and finish 10.41 miles. Since school is over, I made it a goal to run double digits every day. It was hard... but not impossible.
The important thing about continuing your training on the second day is to persevere. It takes a little to run one day, but to run on the second day takes more out of you. On the second day, your mind is a little weaker, and you don't want to work as hard. You've done the hard work on the first day, and on the second day, you want to take it easy. In order to get through that, you need a strong will. It takes a little bit to start, but a lot to keep going.
One way to get through it is to let other people know about what you're doing, the more you let others know what you're getting yourself into, the more you'll actually be 'forced' to do it. Putting proper pressure on yourself will in turn help you to continue to push forward. When you can't go forward with what you aim to do, work to get something to give you that final push.
Find the push and you'll be able to continue forward on your journey. Sometimes, the push is within you, and other times, it'll be something outside. Once you figure that out, the second day won't be so bad.