getting in the Christmas shopping spirit

Don't get me wrong.  I have no problem getting into the Christmas Spirit.  What I am having trouble with this year is shopping for Christmas.  First of all, I hate shopping.  Second, two of my kids will not be here for Christmas.  Yeah, yeah, I know that I am blessed, that I have been given the best gift, and that other mothers wished that they could have two missionaries, BUT, that doesn't stop me from being sad.  I am sad in the stores.  I try to find stuff to send Kade in his box, and find myself tearing up and not accomplishing anything.  I just went through this a couple of weeks ago trying to get Destinee's box sent off to Guatemala.  Why is it so easy to be sad and yet happy at the same time?