While waiting for the Boston Marathon to start, my boyfriend and I pondered why we run these races. Standing in the cold with thousands of other runners, our discomfort got the best of us. “Well, let’s see how we feel at the end,” I said. “Maybe by then we will have remembered.”

It’s hard to know what perspective I can add to what happened on Monday. Neither I nor my loved ones were harmed. And clearly those who suffered injury and loss will feel the impact far beyond what the rest of us can comprehend. But I can share my experience as a runner.

Running Boston is the highlight of many a runner’s career. Merely qualifying is an accomplishment. For example, I had to run the 26 miles and 385 yards faster than 3:35 to get in. Then there’s the fact that it’s the oldest annual marathon in the world, and one of the six World Marathon Majors. I wasn’t sure I’d ever get the privilege to run it, but I made the cut last year in Los Angeles, by 39 seconds.

Still, I don’t think I was giving Boston its due. Probably because I’ve got my eye on a longer race later this year, I hadn’t committed fully to the training. I wasn’t sure my heart was all in this race.

After Eric, my boyfriend, went off in the first wave of age-group racers at 10 a.m., I followed in the second wave, 20 minutes behind. Once it warmed up a bit, it was a glorious day — perfect for running — and my appreciation of the Boston Marathon began to grow. I moved along at a good clip, thinking about my friends and family who were just starting their day back on the West Coast. Maybe a few would even check in on my progress.

I made good time during the first half of the race, but by mile 18 the pain had set in to my hips and knees. To post a good finish, I would have to grind out the final 8.2 miles, using willpower and the cheers of the incredible crowds as my fuel. Throughout the race, I kept marveling at the spectators’ goodwill. Then I remembered that I’d been in their shoes before. Both roles are incredibly rewarding — to give and receive support, to and from strangers.

The finish line was a blur as I cruised across it just after 2 p.m., with a time of 3:43:36. Elated but dazed, we runners stumbled down Boylston Street to pick up water, food, blankets and medals.

As we runners approached the yellow school buses that held our belongings, we heard the BOOM! We were concerned, but we didn’t know what make of the two loud blasts a few blocks away. Maybe it was celebratory fireworks? Then we saw the smoke and knew something was wrong.

I made my way out of the area and ran into Eric — lucky because he was supposed to have waited for me in an area that was now inaccessible. Emergency vehicles raced by. What to make of it all?

We held onto each other tight and found our friends who had come to cheer us on. With little information about what was happening or what to do, we found our way to a T station to head back to Cambridge. Neither Eric nor I had our phones, but our friends did. They posted a photo of us to let everyone know we were okay.

By the time we got back to the apartment where we were staying, Facebook was filled with messages of concern from our friends. We quickly posted updates and received an outpouring of support.

Eric and I both work for Facebook. I’m not sure we fully realized its power until today. I was surrounded not just by real friends next to me, but also by hundreds more through Facebook. These Facebook friends posted comments to our profiles, “liked” our status updates and sent me messages because they saw my name among a list of participants from Menlo Park and wanted to check on me. One friend used Facebook’s graph search feature to find all “my friends who live in Boston” and account for them.

I returned to my question from Monday morning: Why run the Boston Marathon? Of course I love the feeling of accomplishment, but now it seems wrong to celebrate in the face of what happened.

What seems right, though, is to celebrate the support and love that I felt and I saw, especially after the race was marred by the violence. This is another reason why I run these races. Training can be very solitary. So can life.

On race day we come out and share our love of running with each other and with the world. It’s an awesome thing to behold. After Monday, I’m more convinced than ever that we should continue, and with even greater fervor.

So, see you at the next start line.