"No one tells you how quickly dogs age." The unique sadness of watching your dog grow old.

It’s a difficult moment realising your dog is ageing.

Everything becomes slower, but it’s hard to explain.

A Facebook post about the pain of watching dogs age has gone viral, as the author articulates the unique sadness of seeing the pet you love grow old.

In the post, which was published on Juniper Fox, the writer describes the way a dog’s eyes become milky, and the fact that they take longer to respond when they’re called.

“No one tells you how quickly dogs age. How one day you wake up and suddenly their face is all white, how their eyes start to seem more milky than before, how you have to call their name a few more times than you used to,” the writer began the post.

Did you know dogs can tell when you’re upset? Post continues after video. 

“People tell you not to blink when you have children, but what about the dog who was with you before your children were even thought of? The dog who was by your side before you found the love of your life, the dog who jumped from apartment to apartment in your early 20s. No one tells you to cherish every moment you have with them…” the author added.

“Cherish the dog. The one who’s been there through every break up and every dumb fight with your best friend. That dog who slept in the bed with you when you were lonely and made you feel safe when you left home. Cherish him, because one day you’ll take him on a walk and he’ll start to get tired before you and you’ll realise just how many years he’s been walking by your side,” the author finished the post, before adding a photo of their dog in the forest.

The writer put into words what so many had felt before, but that so few had been able to articulate.

The post, unsurprisingly, went viral, being shared over 85,000 times, with Facebook users sharing their own stories of grief.

In the comments there are tales of dogs standing by their companions through family deaths, anxiety attacks, and the other harrowing moments of life.

There is no loyalty quite like that of a dog.