I've recently come up with a brilliant idea (although I'll concede that many others have done this before me).
When you need some cheering up, all you've got to do is google "puppies."
"Cute puppies" works, too. Or even "lab puppies" if you prefer those. Choose your breed and get googling.
Warning: puppy googling has the potential to increase depression and discouragement if you do not have a puppy and really really want one. Proceed at your own risk.
Here are some puppies that I liked: