Until now your pup has usually had some form of company during both the day and the night; whether that be in the canine form or the human form will not matter.
Puppies sleep a lot - a huge amount of their day is spent sleeping so it's not just about where are they going to sleep overnight but also where might they sleep during the day - is it the same place or different places?
You can take advantage of the amount that they sleep by teaching them it's okay to be separated from you - whether that's in the house or when you leave them at home and go out.
When I consult for separation anxiety issues, most often than not the family are unable to be in another part of the house without the dog always having access to them. However I have seen people able to be in another part of the house e.g. upstairs; but unable to leave - this is where they have taught the dog to sleep away from them, or not come upstairs but they have not applied the same teaching for when they leave the house. I wonder whether we as humans think that it's different if we remain in the house compared to leaving it - so we therefore act differently in teaching what is effectively the same action - leaving the dog/pup on it's own for a while.
So I figure that if you can separate the pup from you in the house you are going to have a much easier time of being able to leave the pup to cope without your company in the house.
When we first bring a pup into our homes we should remember that while at the breeders (talking responsible breeders here) the pup would probably not have had human company 100% of the time; yes probably the pup would have had canine company but there is a difference. So we should carry on what the breeder has started, what the pup is already used to!
What I think are ideal things for a pup to learn so that it does not get stressed when left alone are:
That it is okay to be alone.
Their family will come back.
The pup can amuse itself when the family is there or not.
That it can rest/sleep whether the family is there or not.
That being behind a door or a barrier or something similar is okay and actually could be rewarding.
I am lucky in that I was able to change my career in order to spend more time with my dogs. Over the years the new career has developed within different environments and scenarios, with the latest one being my dogs not only get to come to work with me but they get to learn how to be separated from me there as well as home and without stress!
I barrier train my dogs. What I mean is I teach them that being behind a barrier is a great place to be; the barrier is usually some form of puppy pen but I will use one that my dogs can easily push aside or even jump over if they so wished. But I also laid the workplace out so that barriers were also glass paneled doors as well as solid doors and I have baby gates across some of the doorways too. Wherever my dogs are they are generally happy being there. Like many dogs they would prefer to be next to me at all times but life doesn't make that feasible so I teach them how to be okay about not being close to me sometimes even if they can see me.
In talking to people that have pups or dogs that can't cope being left I do actually believe it's the humans that have more trouble leaving the pups than it is the pups themselves. This could sometimes be true of older dogs, rescue/rehomed dogs too - these dogs are really smart in that they learn really quickly so if when they go into their new home they aren't left alone they think that's how life now works.
Dogs live in the moment, what happens to them when they are young helps shape their reactions to life but I don't believe they really think about yesterday or tomorrow - just what is happening right now. So if you bring a new dog (whether pup or older) you need to help them learn that it's okay to not have access to you all the time.
When do my own dogs not have access to me while we are all in the house:
If I put the rubbish out
Sometimes when I need to answer the door
If I have a visitor who is uncomfortable around dogs
If I need to rush up or downstairs and want them to wait where we were.
Sometimes if I am preparing food in the kitchen and don't want them underfoot.
At the moment we have a lodger who has dogs so we have a couple more barriers just so the dogs have some time away from each other (also because one is a destroyer of toys and mine are not) - all of these dogs get on well together, can even lick off the same plate together. Just sometimes we need to stop them from playing constantly.
So the big question is - can you separate yourself from your dog within the house and everyone is comfortable (including on the same floor of the house)?