Hi ho, hi ho, it's back to work I go

Boo hoo, sniffle, sniffle. Friday was my first official and full day back to work after this wonderful summer. Today was the first day of school. I spent a while sobbing last night and had to choke back the tears several times this morning and again this evening when I put the babies to bed. They go to bed so early (which I don't want to mess with because they are sleeping through the night) that I only get to see them for a little over 2 hours when I come home from work. I know they are being well cared for...there's no one better than Daddy (except me of course, he he) to be with them all day. I know they know I love them to pieces. I know this is what's best (and financially necessary) for our family and in that way I'm caring for our babies in the best way. BUT - I'm experiencing what I can only imagine is the "guilt of a mother" in a big way. How do I do this? How do I give 100% to both "jobs"? How do I "turn off" work mode when I come home? And if I can't, does that make me a bad mother? See? It's mommy guilt. Of course I will survive this and it will get easier with time. Right now though...not so fun.