Editor's note: John Farah is the co-author of "Let's Pick it up a Bit," a memoir and a guide to help people lead an active life. This year will be his 19th Boston Marathon.
(CNN) -- "Twenty-nine minutes for his first five kilometers -- he's right on schedule," Nelson Williams excitedly announced to my staff at Enspire Dental in Ann Arbor, Michigan.
Nelson and I had a plan for the 2013 Boston Marathon. I was to run every 5K in 30 minutes. The goal was to finish the marathon in four hours and 15 minutes.
Not being in top form at the forever-young age of 70, I thought the pace was doable. Not easy, but doable.
No one at the clinic knew the plan. Nelson and I kept it a secret because the staff had contributed to a pool -- each person predicted my finish time, and the one who came closest won all the money.
"59:30 at 10K. Perfect," Nelson relayed.
The real-time updates got everyone into the action -- though the money on the line probably helped. Nelson acted like a proud coach whose student was finally following his advice.
"Three hours and 32 minutes at 35K," he shouted. "He's going to do it. It's mostly downhill from here."
Nelson was grinning from ear to ear, running from one end of the clinic to the other, keeping everyone updated. Every staff member believed they could win this thing; even some of the patients were in on it. They were captivated, charged up, cheering me on.
"Four hours and four minutes at 40K," Nelson shouted. "He has 2K to go; it is just over a mile."
And then... nothing.
Nelson said nothing. Everyone had their eyes on him, waiting for the final update.
Nelson knew something was not right.
"Something happened," he said. "He should have finished by now."
Everybody was quiet. Seconds ticked-off.
My assistant, Debbie, got on her iPhone and checked CNN.
"They are saying that a bomb went off near the finish," she said, her voice cracking.
They all stared at each other. No one said a word. She must be wrong, they thought. This just doesn't happen at marathons.
Then the phones started ringing. Nonstop. Patients, friends, relatives, more patients -- all calling the clinic inquiring: Was I OK?
No one could give them an answer. Time passed. By now, it was clear that two bombs had exploded and many people were injured, some severely.
Unbeknownst to anyone, I was the first person the cops stopped less than two blocks from the finish line.
My wife Jackie and her daughter Erin were waiting for me directly across the street from the first explosion. They were luckier than many.
It took more than 80 minutes before Jackie and I connected.
We flew back to Detroit that evening shaken but physically unhurt.
I could not sleep. I kept hearing the sirens blaring all night. Images of ambulances carrying the injured raced uninterruptedly in front of me.
It was surreal.
On Tuesday, April 16, I went to work. I always did after Boston.
It was difficult, very difficult. But I had patients and staff who were waiting for me. The phones continued to ring, but now staff had answers. I treated patients, but emotionally I really wasn't there.
When they asked me about Boston, I choked up. It was hard to talk about it. It had affected me like nothing else before.
I still don't understand how malicious and evil some people can be. My consolation is that the majority of people are decent and caring individuals. I'm an optimistic person, and I have faith in the goodness of humanity.
I have to; I have no other choice.
So many people reached out to us after Boston. The outpouring of concern and support from patients, friends and acquaintances was overwhelming. They all care; they all love; they all feel. They all remind me how good people can be.
That is what makes me want to go back to Boston. Yes, like thousands of others, I'm running Boston again this year. Every marathon is a marathon, but Boston is Boston.
I'm running it to make a simple statement: Acts of cowardice will not stop me from exercising my rights as an athlete and a human. I am running it for those who were injured and can't run it. I am running it for the love of running. I am running it to show my support for all Bostonians.
Lastly, I am running it because in 2013, I never really finished.
This year, I will.