Working Mom: Any Hope?

Just after I went back to work (after Emily), I was talking with two other people about kids and raising them: pitfalls, etc. We represented a full time mom, part-time working mom and then me a full time working mom. The full time mom started talking about how she couldn't see how a working mom could do everything a child needed because they weren't there for so much and when they got home they were tired. She was talking about kids, home, husband etc. I don't believe she was meaning to be malicious. She was overwhelmed with everything on her plate and she just couldn't see how you could add in work and keep up with it all. I was hurt, and worried. I'm a full time working mom who feels guilt about all of that every time I walk out the door to work and during every meeting that doesn't allow me to get home right after school. Even being home everyday for the last 7 months hasn't relieved any guilt. I have a very precocious two year old and a beautiful baby boy. I'll admit I'm scared to go back to work. I haven't been able to keep up with everything (kids, house, husband) and I've been home each and every day. Now I will be gone between 7-9 hours a day, four days a week. Not counting the reading intervention practicum work that I have to get done by March. I think back to that conversation and worry, do my kids have a chance? I've been reading a parenting book because I realize that I have no idea what to do with Emily. I'm tired of being frustrated with her behaviour. I love the book and have gotten great suggestions, but its added to my guilt. It describes three parents which are all behaving in different way that stifles a child's personality and can lead them to feel bad about themselves. I am doing two and half of the behaviours! So much to work on. Do my kids have a chance? They have their dad and grandma to look after them while I am gone, and both love them as much as I do. But is that enough?