What makes a "good" mom?

I was asked recently to define for myself what it means to be a good mother.  I was asked a week and a half ago, and I have still really, really struggled to figure it out. To be honest, in most aspects of my life, I'm a pretty competitive person and I struggle with comparing myself to other people. But in this example, I don't really compare myself to other moms and I really do focus on what makes me feel like I'm being a good mother. And honestly, I still don't know what it is.

Could this possibly be why I often feel like I'm failing?

Growing up, my mom always said, quality over quantity. She was a working mom and she was not able to come into the classroom all the time, although I don't really remember the other moms that did but I suppose they were there.  I do remember that she was always there for field trips and special events and things like that. And part of me knows that that is what I need to do, but the other part of me thinks that I just want to be at everything. I don't want to miss a minute if I can help it.  On the other hand,I like not being with my kids sometimes, I like the time off and the break and moments to think that work often provides. On the other hand, I don't want to miss anything at all. And at this point I think I've run out of hands. 

I struggle with this partly because I think it's good for the kids to have other people, or go with friend's parents, or to have someone else take them somewhere or watch them.  I have fond memories of riding in the back of friends' parents' station wagons or mini vans.  I don't remember what we were doing or where we were going but I know my mom wasn't there.  I actually think it's good for them and so, in a way, I think I'm being selfish to not want that.

My goal as a mom (because you know I love to set goals) is that my kids are independent and they can go around the world and feel comfortable to follow their dreams.  That they're kind and compassionate people.  Of course I want to achieve this by never letting them go and tucking them in every night for as long as they let me.  I want to read them books every single night.

What I think it really comes down to is that I want to be reliable.  I want them to be able to depend on me.  I want them to know that if I make a promise, I will keep it.  I just have to figure out how that actually translates into every day actions. So, there you go. I figured it out.   Except now I think I have more questions than when I started.  

Like what does reliable look like to me and how does that differ from a 4 year old?