Last year, when  my kids were both at school, I would get lonely at home sometimes.
I can understand that. It's usually either parents are happy they are out of the house, 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. 
It's weird how they can drive you crazy when they are with you but you miss them the minute they are gone!
Yes it is. My youngest has been away all this week for his first summer camp. It's been both awesome and lonely. 
They finally go back to school next week and I'm looking forward to it but I know I'll get lonely at times.