My heart both rejoices and breaks every year when we celebrate my firstborn’s birthday. I rejoice when I think back to my son’s birthdays when he was 4 or 5 years old. Each year he picked a new theme for his party, reflecting his current passions. One year he loved Blue’s Clues. Another year, trains. The next, magic.

Weeks prior to my son’s birthday, I’d plan fun activities, crafts, games and goodie bags to go with the chosen theme. Yes, I was that mom. Even before Pinterest, I loved collecting ideas of how to make DIY birthdays feel special.

No matter the theme, each birthday party shared one thing in common: a group of friends from school helping my son celebrate his big day. They played silly games in our living room, ate cake on our porch and chased one another in our backyard. Laughter filled the air against the noisy backdrop of the slightly uncontrolled chaos of a kids party. To see my son’s face light up, to know he felt valued and accepted by his friends, to hear the shared laughter—that was a birthday gift in itself.

Flash forward to middle school. Around sixth grade, we began to notice my son’s friends drifting away, one by one, like balloons floating away, forever out of reach. They stopped inviting my son to their birthday parties, to the movies or to just hang out. By high school, social invitations ceased to exist. Not only did my son’s old friendships fade away, but new friendships weren’t taking their place. A gaping social hole existed in his life.

What happened? Around ninth grade, we discovered that my son—always a shy, socially awkward kid—has Asperger’s Syndrome. He’s a talented artist and a smart kid. Although quirky, he was so high-functioning that we didn’t connect the Asperger’s dots until high school. With social and communication difficulties at the crux of Asperger’s, this Autism Spectrum Disorder often spells “death sentence” to a child’s social life, and it delivers a devastating blow to self-confidence. Being socially awkward and missing out on the hidden nuances of body language, facial expressions, and social cues, people with Asperger’s struggle to connect with others, making it difficult to make and keep friends.

This brings me to the bittersweet tinge of celebrating my son’s birthday. Every year birthday parties have gotten smaller. In preschool, a dozen or more kids filled our back porch at birthday parties. By middle school, we could fit all the party guests (including our family of four) in our van. The last birthday party was an awkward gathering with two friends who knew (but did not like) each other. Those middle and high school years pummeled my heart, making me cringe at the shrinking circle of friends who no longer issued or accepted party invitations.

I am mourning the birthdays of yesteryear filled with two dozen cupcakes, party bags, Pin the Tail on the Donkey and squeals of laughter. I am yearning for the days when my son felt accepted and included by his peers. I am missing the days when birthdays felt like the celebrations they should be.

As my son’s birthday approaches each year, I still cry a little inside for what should be the happiest day of the year for him. Parties once populated by friends have been replaced by family-only celebrations.

But I also celebrate my son—now 19 and in college—as he prepares for the next phase of his life. I am in awe of the man he is turning into, as I watch his self-confidence slowly rebuild. I silently thrill at the flicker of college friendships beginning to take shape.

Birthdays serve as bittersweet reminders, now and forever, to be my son’s best friend, regardless of whether or not anyone else steps up to fill that role.

This article originally appeared on the blog Grown & Flown and is republished with permission. Lisa Beach is a freelance journalist.