Working mommies

How many of you moms on here work full time jobs? I myself am a single first time mommy but I work a full time job so my LO is in full time daycare. I hate being away from him all day every day but it's what I have to do to care for him. Lately, especially after a comment from a relative, I am feeling like a complete failure as a mom because I spend so little time with my LO...anyone else ever feel this way? What did you do to help yourself get over that depressing feeling of failure? Also, how common is this if it is at all?