history: When my kids are in school all day I get lonely sometimes. Last year_comma_ when  my kids were both at school_comma_ I would get lonely at home sometimes. I can understand that. It's usually either parents are happy they are out of the house_comma_ or sad that they're gone. I'm sorry you feel lonely.  Most of the time I'm happy and content but occasionally I get lonely. I can understand that. Kids have a big presence and their energy creates a void. Hopefully you can find things to take your mind off of it. 
current: It's weird how they can drive you crazy when they are with you but you miss them the minute they are gone!
next: Yes it is. My youngest has been away all this week for his first summer camp. It's been both awesome and lonely. 