If you are a multi-dog household ..... don't forget that your dogs need to learn that it is okay to be without each other as much as they need to learn they can cope with you being absent as well.

Pro-K9 receives numerous 'cries for help' from people who have two or more dogs and have never had one anywhere without the other.  Then circumstances change.  Sometimes this is due to a necessary stay-over at the Vet, or because the owner for whatever reason can no longer keep both dogs, or because one has, sadly, 'crossed the rainbow bridge'.  The dog left behind (and who knows - perhaps the other dog having been re-homed) pines - becomes destructive; barks excessively, becomes depressed and/or is generally moping for a considerable period of time.

Train your dogs for independence.  Independence from you and independence from their other 'buddy'.  It is most ideal to prevent dependancy attachments BEFORE there are problems.  So from the 'get go' you can start by sometimes (eg) training the dogs separately from each other; walking them separately; doing other things with each of them singularly. Randomise what you do - sometimes they are out together, sometimes they are not.  

If however one or both of your dogs already show signs of distress at being the one left alone, it is adviseable that you contact your behaviourist.  In cases such as these a program can be devised so that the animal's stress is minimised and 'learning' is possible.  Time periods for being alone are gradually increased as the dog learns more and more to cope with being by his or herself.  If the attachment is dog/dog you might be able to begin independence training from each other by having one person take one dog and another person remaining home and playing with the other dog.  There are various ways to manage these situations and work towards rehabilitation - each situation needs to be regarded on its own merits and treated individually.  After all, our dogs are all individuals and response/react differently.