"People tend to post only the good things in life. But that's not realistic," he wrote

Tyler Posey
Credit: Tyler Posey/Instagram

Tyler Posey's mom is never far from his mind.

On Friday, the Teen Wolf actor, 28, shared a photo of himself sitting in the grass beside his mother Cyndi’s grave on what would have been her 61st birthday.

"Happy birthday mama," he captioned the photo, which showed a tear running down Posey's face.

Posey then reminded his 5.6 million followers that it's okay to be vulnerable and share hard moments in life on social media.

"People tend to post only the good things in life. But that’s not realistic. Not that this is bad or anything, but it’s a glimpse that life ain’t perfect. And that’s the exact way it should be. Nothing is perfect. Long ago someone decided 'happy' is the way to be. I’m very happy. But you can’t deny the other things," he wrote. "I think people are searching for 'wholeness' or 'completeness' and in my opinion that is the true 'happy' but it’s okay to get that confused. You can’t be whole with out the ups and down. Here’s to all the fallen and the loved ones who can’t share this beautiful day with us in person."

He concluded: "Thank you for reading and coming on this journey with me. LOVE is what matters most."

Tyler Posey
Timothy Norris/Getty

Cyndi Garcia Posey died at age 55 in December 2014 after a four-year battle with breast cancer. Posey previously opened up to PEOPLE about coping with the loss, saying he and his family struggled for a long time.

“When my mom passed, it hit us hard,” he said of Cyndi, who had homeschooled him and served as his business manager when he was a child star filming movies like Maid in Manhattan. “She was my best friend. She was the glue that held our family together."