Sometimes regret is a slow trickle of subtle feelings, which eventually gather into a big, dark, heavy cloud inside.

My best friend from college got very sick after she had her baby a few years ago.

We had stayed in touch and had a special bond that forever secured a place in our hearts for each other, but after a decade of being out of college, living on opposite sides of the country, and running around our busy life adventures, we weren’t as close as we once were. It took me a while to understand just how sick she was, and even longer to go and visit her during a business trip that brought me near her home.

I checked up on her in the following months and years that it took her to finally recover, and went to see her a few more times, but when I looked back at those years recently, I felt that big, dark, heavy cloud of regret inside:

I hadn’t been a very good friend. I could have done a lot more checking in and visiting, and I should have.

Regret is one of the most painful emotions, at least for me. And I think, in part, what makes it so painful is that we feel it about something that happened in the past, something we’re unlikely to be able to do much about. Regret comes with a tinge of hopelessness.

There was no way I could go back and be a better friend. And I definitely spent some time engaged in the unproductive act of beating myself up for not being a better friend. But what I could do was be a better friend going forward -- to my best friend from college and other friends in my life. I recently took her to Chicago for the weekend to see one of my favorite singers, who was performing there. It was an amazing two days of catching up and being together, and I think each of us found a lot of healing in that.

But sometimes regret doesn’t take years to show up. Sometimes it smacks you right in the heart.

Last week I wrote about the incredible beauty and power of taking time to connect with people we encounter in the course of our days and lives. I mentioned a little boy I recently met on the train platform, who was there to watch trains with his dad. His pure excitement at the fast speed of Acela broke through my tendency to take those rides for granted and filled with me the warmest sense of gratitude as I rode the train from Boston to New York.

What I didn’t write about is that as soon as I said goodbye to the boy and got on my train, I felt this pang of regret deep in my gut:

The boy was dreaming about going on the fast train. His dad had even asked me if the tickets are expensive. Why didn’t I write a check for the boy and his dad to go on the Acela to and from New York right there and then?!

The doors had closed and we were moving away from the platform by the time I realized that what I wanted to do most at that moment was to turn back and help make this boy’s dream come true. But there was nothing I could do: We were already moving and I had no way to contact the boy or his family.

I had two very busy days of work in New York, but I couldn’t get the boy and his excitement about trains out of my mind. The feeling of regret at not having done something was growing too.

When I got home, I started to make a list of ways I could try to find him: get a journalist friend to write a story in the local paper, make a short video and try to get friends on social media to spread the word, etc. My husband suggested that I go back to the station and ask around -- perhaps they’d come before and someone would know them.

So I did. When I started to tell the ticket agent about this boy and his dad I’d met on the platform, her face melted into a wide smile.

“Oh, I know them!” she exclaimed.

I think I jumped and hit the ceiling when I heard her say that. OK, I didn’t, but I did start crying. And I’m not really a public crier.

"You do?!' I shouted excitedly.

“Yes, yes, I know exactly who you are talking about. It’s his grandpa, actually, who brings him on most holidays when he is watching after him. They get ice cream and then come watch trains for a while. The boy loves them!” she continued.

I was beyond myself. Marlene -- that’s her name -- took all my information and promised to pass it to them the next time they came in.

“Please tell them I am not some weirdo,” I pleaded with her. “I was just so taken with the boy’s pure excitement about trains and it reminded me, in the best way, not to take even the most regular things for granted, like taking the train for a business trip.”

“It would be such a gift to me to be able to pay for him and his grandfather to go to New York City for the weekend and take the Acela both ways,” I told Marlene.

I am crossing all my fingers with hopes that they will come back soon to watch the trains and that it won’t be on Marlene’s day off, so she could talk to them and give them my information. I hope they don’t think I’m some weirdo and actually get in touch. I hope I can do this small thing as my gratitude for the boy’s reminder to wake up and soak in all of life, including the parts that can often be exhausting, or boring, or just regular.

There’s often nothing we can do to go back in time and undo whatever we did that we regret, or do something we wish we had done. But I think there’s always a way to do something going forward.

So I’m really hoping I get to do this one thing. C’mon, universe, help us out here, will you?:)