Should I put my dog to sleep?

Thing is my dog, Snoopy broke his right front leg on Thanksgiving, but we got him all fixed up with his cast and he was recovering real well. Today in morning Snoopy for some reason forgot he still was injured and took a jump of the sofa. And broke his left front leg. We just got back from the Vet and he has a cast on both legs now. But I see him struggling to move and all. Its just painful to see him just ly there not being able to get up. The Vet told me to consider just putting him to sleep, but I'm not sure? What should I do?