The most meaningful day

The most meaningful day

Mateo Osorio

Jan 20, 2026

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This email is scheduled to get sent at 9:30am on Tuesday, January 20th. It’s scheduled because at that time, I’m going to be in the depths of the UCSF Neurosurgery building under general anesthesia.

So even though I’m not around to press the send button while my mom is biting her nails in the hospital waiting room, I still wanted my friends and family to get a nice note from me, letting you know that everything is going to be alright :)

December 8th is now the most meaningful day of my life. Felipe, my father, died on that day 9 years ago. Every year since, I’ve done something to remember in his memory. His birthday, September 26th, is usually the date where I do something grand - a huge steak, a cookout on the beach, an incredible bottle of wine with friends (as if I know a red from a white) - the type of stuff that fueled his contagious smile and he’d enjoy.

But on the anniversary of his death, I tend to do something more private. Sometimes I barely even mention it to the people around me. I may go on a run and look out at the sunset over the ocean while thinking of him. I may write him a note. He doesn’t leave my mind all day. I’ve missed him more and more as the years gone by, even though his face is starting to fade a bit from my memory if I don’t look at some old photos.

A month ago, on December 8th, as I was finishing work and thinking about what small gesture to do that day for dad, he was the one that me a message. He sent me to the hospital.

From one minute to the next, I experienced the most intense, world splitting pain I’ve ever felt. A migraine so strong I wanted to bash my head into the ground. I couldn’t bear to exist. I couldn’t stop crying, laying on the ground with the lights off. I had trouble breathing from the emotions gushing out of me, and when I called Daph to ask for help, the words would not form. I had. To. Speak. One word. At. A. Time.

I say it was a message from my father because the doctor in the emergency room told me I’m a lucky man. The episode I had (a type of seizure) was not due to a stroke, or internal bleeding, or something critical that needed immediate care.

Instead, it was because of a large mass in my head, a tumor that’s been patiently, slowly, quietly growing for years. In that time I’ve been travelling the world. I work a demanding, stressful job, I play soccer, tennis and volleyball, multiple times a week. I ran a half marathon three weeks prior, right before going hiking in Patagonia. People around me wouldn’t say Mateo takes it easy.

Yet somehow, for some reason, on December 8th, the mass did something to my brain to trigger the seizure, making me go to the ER, where the doctors immediately found the tumor. Yet it didn’t do something bad enough to make me lose one of my senses, impact my mobility or memory, nothing. A week after my diagnosis, I flew to Colombia. I ran for an hour in the sun, feeling totally normal.

I’ve been a skeptic my whole life. The engineer in me doesn’t trust anything that’s not peer reviewed. But in this past month, perhaps the most introspective and thoughtful month of my life, I’ve come to believe that there is more to life than coincidence and the scientific method.

The message from the universe could not have been clearer. *Mateo, you need to see a doctor right now.* But it didn’t harm me. Quite the opposite. The tumor could have easily kept growing for months and months, eventually getting to a point where the conversation with the neuro-oncologist would be very different.

I now listen to my body. I pay attention to the signs. Lean into feelings, and try and understand what they mean. I’m not suggesting you should start interpreting the palm readers literally, or frame the Chinese fortune cookie paper and get it tattooed. But I’m listening, and I’m noticing the universe, even the one I can’t see or touch or feel, is talking.

And in a few hours, when I come out of the surgery room and wake up tumor-less, I’ll have my ears more open than ever. I’m excited for what life will bring.

Thank you to the countless people that have been on my side - on my team - for the past month. I could not have done it without you all.

For the people who are hearing about this for the first time here, 1) sorry! lol. 2) I promise I’m ok. I’m in the hands of one of the best doctors in the world, who is currently opening up the noggin and removing the tumor. I’ll be home in 1-2 days with some Tylenol and a gnarly scar, but that’s it.

If you want to keep updated on how it goes (instead of relying on the extraordinarily infrequent substack posts, which I’ll send at some point but no promises), you can join

this Whatsapp group

.

In a few weeks when pathology comes back and my doctors have a better idea of what this thing they’re removing is and what it means for the future of my already mediocre tennis and bad sense of humor, I’ll update people in the group.

Call your parents and tell them you love them.

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