It's been three years, and I can still remember the desperate feeling as I frantically dashed into my son's preschool classroom and saw him sitting there—all by himself.

It was late December, and my son's class was having a cookie decorating party. Every other student had a parent, grandparent or someone special sitting beside them. All my sweet son had in front of him was a messily decorated cookie that I should have helped him decorate. But I didn't, because I wasn't there. I was a no show.

I hadn't lost track of time, misplaced my keys or gotten stuck in traffic. I had just plain forgotten about it. And as I looked at my son sitting there alone, my mind raced, thinking about how he must have felt when all of the other adults walked through the door to greet their kiddos, but no one ever came for him. I felt helpless. The party was over, and there was nothing I could do about it. Nothing I could do to make it better, for him or for me. I walked up to his table, wrapped my arms around him, and burst into tears.

As we were exiting the classroom, the preschool director noticed my distraught face, walked up to me and gave me a big hug. Then, she spoke:

"I need you to try and not be so hard on yourself, okay?" she said softly and sweetly. As I continued to sob and blubber on her shoulder, my eyes closed, and I managed to get out a weak and unconvincing nod in agreement.

I walked away from that experience with two thoughts:

1. Yes, I needed to stop being so hard on myself. As mothers, we ALL need to stop being so hard on ourselves. We are human. We are going to mess up and disappoint our children from time to time.

2. I still needed to cry.

And that's what I did. For a week straight. I cried. Every time I thought about running into that classroom. Every time I thought about my son sitting there alone, my eyes filled with tears. It was uncontrollable and unrelenting.

Let's be honest. As my son sat there without me in that classroom, the only thing he was probably wondering is when he could eat that yummy decorated cookie. He never cried. He didn't look upset, and he never mentioned anything about it to me. He was fine—and deep down, I knew it. His reaction and grace helped me feel better.

But I still cried.

I posted about my sad experience on Facebook and soon realized that I wasn't alone. Many of my mama friends shared similar stories about times they had "messed up" and the guilt that followed. Some were still dealing with that merciless mom-guilt. For many, the memories were still fresh, and the feelings were still there.

The stories I read helped me feel normal. They helped me realize that I wasn't alone and that we all have those moments that we can't forget, or that we wish we could do over. Those moments, big or small, stay with us because we are mothers who love our children and never want to play a role in needlessly disappointing them.

A few years ago, actress Busy Phillips posted an emotional video to her fans, tearfully telling them about how she and her husband had accidentally left their daughter's beloved teddy bear in their vacation hotel room. You could see the desperation and exhaustion in her sad eyes as she recounted the story. After calls to the hotel and a frantic suitcase search, Busy had to face the fact that her daughter's precious bear was most likely gone forever. She acknowledged that it was just a stuffed animal. She knew that there were bigger things in life, but she still cried. And I cried with her. I'm pretty sure every mom who saw that video was swimming in a puddle of tears by the end of it. I felt for Busy so much at that moment and wanted to reach into my phone and give her a big hug in brokenhearted mama solidarity. I SO got it. Because I had just experienced my own version of it.

For Busy, it was her daughter's teddy bear. For me, it was one forgotten preschool party. But those moments, however small in the grand scheme of things, broke us.

Those moments—those disappointments—mattered to us because they mattered to the ones we love the most—our children.

When I think about that time in my son's classroom three years ago, the tears don't flow like they once did. But it's still with me, and I think it'll always be there. And that's okay. I have forgiven myself, and part of that comes from knowing that I'm not alone. The guilt after those mess-ups is real, but so is the camaraderie I have with all the mothers out there who have been there as well.

We are going to disappoint our children. We are going to mess up—and when we do, we need to forgive ourselves. But while we are on that journey to self-forgiveness, we also need to know that it's okay to cry.

Get it out all. Because we are all mamas who have been there before, and we are all crying right there with you.

P.S. Busy found the teddy bear!