Though I could easily come up with many excuses why I couldn't and shouldn't run a marathon this upcoming July, I choose to focus on the reasons why I can and will:

Beating my previous marathon times of 7:17 and 5:54 is a must. I am determined to run this one in 4:45.
Training for a marathon gives me the opportunity to practice leading the most important person I will ever lead...myself.
Completing a faster marathon at 33 than I did at 24 and 29 would be very encouraging to someone like myself who is starting to feel older and older.
Encouraging Spencer and AJ as they train and watching them cross the finish line, at their first marathon, is more fulfilling to me than completing my own.
Challenging myself to accomplish something that is intimidating to me gets me out of my comfort zone is good for my personal development.
Running long distances, like nothing else, strengthens my inner will and resolve. If I ever want to become a great leader, I am going to need major resolve.
Enjoying the beauty along the various trails, breathing in the fresh air, and feeling my heart pumping as I run invigorates me and makes me feel truly alive.
Learning lessons about life as I run has been very profitable for me. Running is a relentless teacher.
Adding another medal to my collection is always rewarding!

The beauty of well thought out, articulated reasons for pursuing a goal is this:

When strong reasons are juxtaposed to weak excuses, excuses don't stand a chance!