As it was said earlier, you aren't ever ready for your first until you do it. It's like having kids. People tell you what it's like but until you experience it for yourself you don't really know. It doesn't mean you can't do it. And you will most likely make mistakes along the way. But, if you decide to do it and want it bad enough you will make it across the finish line and it was be one of the best feelings of your life.
My story: My wife told me she wanted a divorce in the fall of 2013. She told me I was a fat, lazy, slob during the process. I was 250lbs of unhappy and unhealthy. My life was turned upside down and at this point I had been trying so hard to save the marriage that I had lost myself. I didn't know who I even was anymore.
So, I needed to get back to finding myself. I also wanted to challenge myself and get out of my comfort zone. I turned to Disney for both. I love Disney. I joined this site. I decided that the getting out of my comfort zone was going to be signing up for a Disney race. I knew I would do the work if it meant I could go to Disney. I picked the 2014 Tower of Terror for one simple reason. It was the shortest of the major races. I didn't think I could even do 10, never mind longer. I decided to sign up in March before I had run a step. Then I did a 10K proof of time race in June and as I was running it I decided I could do a marathon. So, I signed up for a marathon in October, just 2 weeks after the ToT.
So, I went from fat, lazy, slob to marathoner in just 7 months. It was hard. I didn't train as much as I should have (one of the mistakes I referred to), and my time was awful as a result. But, I could have quit and I didn't.
Now I am addicted to running. I am doing the 2016 Disney full marathon. And I have set a goal to qualify for the Boston Marathon this year as well. All of this after I turned 40. So you can do this if you want to. You just need to commit, put the time in, and get ready to feel unbelievable when you cross that finish line in January.