Consider the Other Person's Perspective
Think about how your adult child may be feeling about the change and what brought it about. You didn’t fail as a parent because your adult child is returning home; nor did he or she fail as a person. Times are tough and circumstances change in everyone’s life. Be aware of what your new housemate may be sensitive to--or feeling badly about--in relation to the issues that resulted in your living as a unit now. Could be the inability to find a job, a job loss, financial downturn, divorce…whatever it is, bringing the subject up over and over serves no purpose.