That puppy seemed like a great idea at the time, but wow -- he wears you out. Just like humans, pets go through their growing phases, and though it seems like your pup will never grow out of his high-energy, get-into-everything phase, he will mature. Your job is to be patient and provide your pup kind and consistent training to become a well-behaved dog.
When your dog enters adulthood, don't expect that he'll automatically understand good manners and behave exactly as you want. Dogs reach adulthood at varying times; small dogs mature at a faster rate than large dogs, who can take over a year to become fully grown. As they reach their full size, puppies tend to become less excitable and calm down a bit. However, energy level and behavior depend on more than age.
Breed, training, personality and amount of exercise all influence a dog's energy level. Some breeds are more wound up than others -- a border collie is a naturally busy dog, happiest when he has work to do, opposed to the relaxed basset hound. Exercise does more than keep your dog physically fit; it helps him burn energy to calm him down and make him a better roommate. As well, a good bit of exercise before training helps your dog focus and pay attention to the lesson at hand. The earlier a puppy learns what is acceptable behavior -- and what is not -- the more responsive he'll be to you when you let him know it's time to calm down. When you train your dog, reinforce his good, calm behavior so he understands that's the key to your heart.