Unless you have no intention of ever being apart from your dog, then it is a wise decision to train it to be happy while you have periods apart. As we have our pets for many years there will generally be times when there is no alternative but to leave your dog alone or with someone else.
The sooner they become accustomed to staying on their own as puppies the easier it will be for both you and your dog.
It is a lot harder to leave an older dog on it's own if you have never been apart since it was a puppy.
Dogs can get separation anxiety quite easily as they cannot be told when we will be back if ever and they will assume that you have left them and are not coming back.
By training them when they are young they will accept that you will be gone for while and will remain happy knowing that you will be coming back at some time.
I know people who have failed to do this and they have the burden of never being able to leave their dog alone with anyone else.
This can make certain situations very difficult and I have seen these people take their dog to a wedding and a funeral and having to check constantly throughout proceedings to see that their dog is happy in their vehicle while they are gone for very short periods of time.
This is unfair on the animal as there can be times when it is not possible for you to be with your dog, in the case of a hospital emergency as an example.
If the dog is trained to accept these times away it won't be a big deal but a dog who has never been apart from it's owner could be devastated by this time away.
It is in your dogs best interests to get used to time apart so if you haven't done so already, start a plan to help it cope as soon as possible.