I have lost my pet of 13 years and depressed.

I am so sorry for the pain you are feeling. It is unavoidable for anyone who has loved and lost a dog; that doesn't make it hurt any less. Rudyard Kipling wrote in The Power of the Dog, "...I bid you beware of giving your heart to a dog to tear." Yesterday's message in the comic strip Pearls Before Swine by Stephan Pastis was titled "The Plusses and Minuses of Dogs." "Plusses: Friendly, Loyal, Cute, Loving, Cuddly, Fun, Never complain, Protective. Minuses: When they die, they rip your heart out worse than it's ever been ripped out before." Final frame: "IT'S WORTH IT."
When we lost our little senior "foster fail" chihuahua a few years ago, we thought we would go without a dog for awhile, but were inconsolable until we brought home another little dog, this time an adult male chihuahua mix, from a local shelter. He did not replace our "little old lady," but is a tribute to her. This one makes us smile and laugh each day, just like our little lady did.
I hope your circumstances will permit you to have another pet. If you are not ready to take another into your home, I can assure you that there are dogs who are ready to "adopt" you for even short visits. Foster programs permit the best of both worlds--you get to care for a dog in need, typically at the shelter's expense. The last time I checked, shelters were full of pets abandoned for one reason or another, and many through no fault of their own.
I wish you comfort and peace. You have my deepest sympathy. Because I know the experience can help heal the hurt, I hope that you will find the desire some day to dare to love a dog again.

@cabrinik I hear you. Your little dog must have brought you such joy and love over those 13 years. If you are anything like me then your dog was fed and taken care of before you feed yourself. Your little one was such a constant companion for you that it's no wonder you are so sad and depressed. I don't cry easily. When I've lost a dog or cat I've cried my eyes out for days. The loss reaches deep down. I know it's very difficult but please give yourself the time to grieve. What can you do to provide yourself with a memorial of your dog? Would you like to make a picture album? Frame pictures of your little dog to display in your house? Donate to your local animal shelter in honor and as a memorial for your dog?

Say to yourself: How lucky I am to have known this animal that saying goodbye it to was so damn awful!

Dogs are family. Mine have always accompanied me on mountain bike rides, and spend thousands of hours with me on trails. When they reach the old age point and can't come along anymore, it's always hard since being outdoors and moving has been the core of my relationship with them (I'm at that point with the current companion). And when they leave us, yeah, it hurts. You grow accustomed to having them by your side, constantly egging us you with their own enthusiasm. It's heartbreaking when they leave us. I saw a meme the other day about how science needs to quit worrying about smartphones and figure out how to get dogs to live 50 years. I'd be good with that.

I know too well how you feel right now. It just sucks.

Forward could be getting another doggy or a little cat. We’ve down this for decades of our loving doggies. They don’t last enough of we want. My best boy was 16 years old, but his back couldn’t use his walking. His brain to hold, eat.cA great life between us; we set him to our animal doctor and sed to him - my doggy - as his drugs to get closer then he died. We have another one at our house and she is still alive and now 13 yo. We also have another one that both of them play against of who wins. They don’t last as far of an animal life.