At my grandmother’s 70th birthday, my mother caught my grandmother alone for a moment amidst the hubbub, staring into the crowd but clearly lost in her own thoughts. With the thump of the DJ and flashes of moving bodies in the foreground, she asked, “What are you thinking about, Mom?”

“Oh I just can’t believe I’m 70 is all,” my grandmother replied.  “I look in the mirror and see this old woman, but I feel the same as I did at 25.”

She wasn’t bothered, exactly. She was more amazed that this process of growing older actually applied to her, too.

My grandmother was a practical woman, raised on a farm during The Depression in Nebraska. Her disbelief was not an issue of vanity, but rather a moment of clarity about one of life’s inevitabilities.

Somehow she ended up here at a 70th birthday party for an old woman that was herself, complete with eight adult children and dozens of grandchildren running around celebrating the early winter of her life.

When my mom first told me this story, I was a teenager. We were sitting side by side on the barstools in the kitchen with coffees poured and the newspaper spread between us. The concept struck me at the time in an impersonal way. Since most teens can’t actually project the concept of aging onto their future selves, I tucked away the story for later use.

I’m now at an age where I’ve pulled the story out to examine. The impression of my grandma, with her halo of white fluff and papery skin, feeling like her sturdier, brighter 25-year-old self, resonates.

This story has finally become tangible as the woman who looks back at me in the mirror each morning is beginning to change too.

Now I see the starburst of lines around my eyes when I smile, the hard line of my strong jaw and the prominence of my cheekbones. I see the cords of my neck muscles and the vertical indent between my eyebrows. My highlighted, mousy blonde hair is punctuated by some wiry grey.

The other day, I was looking at photos of me from my mid-twenties with my son. I saw myself on the page with my big smile and rainbow eyes, a light spray of freckles across the bridge of my nose and my shiny, golden hair. How did I not know how lovely I was?

“Do I look the same?” I asked my little boy, curious what he would say.

“No.” he simply responded in his unfiltered, little boy way.

Of course I don’t.

Since that time, he has grown from a saucer-eyed little baby into a skinny child with gaps in his teeth. His sister has grown from a newborn with a full head of black fuzz into a feisty toddler. My body has expanded and contracted twice. I’ve missed sleep, I’ve worried, I’ve laughed, I’ve cried, I’ve struggled and I’ve gotten older. The softness of my youthful face and body has given way to a tighter, tougher, ropier woman with some experience.

While I’m sipping my tea and writing this, my telomeres are shortening and biology is at work.

While my grandmother was caring for a family of ten on pennies and faith in the Catholic Church, she stopped producing as much collagen.

Our vehicles for life deteriorate right under our noses, and it’s not in the flurry of days or weeks that we notice it. It is in those little moments that occur over the years: when you no longer get carded, when you start being called ma’am, when you catch your reflection and it’s not what you expect, or when you look out into the crowd at your 70th birthday party and see the literal fruit of your womb grown and on the dance floor.

So what is a human to do with this inescapable fate?

I’m lucky that I have my grandmother as a model. She is 95 now and winter is almost over. Though I bet 70 looks pretty good from where she is sitting, she wears 95 well. She moves at a snails pace with her walker, and the simple tasks of the day consume her physically. Her eyes still twinkle, though, with her century of experiences and wisdom lighting them from behind.

My grandma sees the old woman in the mirror and acknowledges that it’s the right time for her to be there. Because of her, I too will accept the wiser, older woman in the mirror. I will not shun or fight her. Like my grandmother, I will know what I cannot change. As the blonde sheen in my hair dims and the elasticity of my skin goes, my eyes will sparkle more brightly with what I know. The next kind of beauty will emerge, and I’m ready. My grandmother has taught me this.

Guest post written by Libby Galin. Libby is a writer, teacher, yogi and mother of two fabulous children. You can find her in Chicago trying to be peaceful and creative. Follow Libby on Twitter.