Positive or Negative?

As my three girls get older I am less and less required in their day to day lives. Each one is self sufficient and capable and each one is creating or has created a life independent of me. While each daughter is striving to create her own identity I have been faced with the fact that for each of them right now they are the most important person in the world. I have also come to realize that they are striving to know themselves and that they believe they know me.
Here is the rub…me as a person, and who I am as a Mom are two different people. I realize that my children think they know me but reality is that they just don't. The other reality is I probably really don't know the people they are once they go out in the world. It is easy to stay focused on the child within them and think that this is who they will always be, but the truth is life is going to grab a hold of them and shake them around by the scruff of the neck. My neck is still sore from some of the shaking life has put me through. How do I prepare these children of mine for this shaking?
The other night I was commenting about something going on in my life and my oldest daughter replied something back to which I made another comment explaining my feelings about a somewhat inane topic, my daughter then said "I was just trying to be positive, that's how I am". All I really heard her say was "geez Mom you are such a downer!" The odd thing is that I did not think I was not being positive, I was merely expressing the simple fact that I was disappointed we had purchased a smaller size water heater, but it had to be done, we needed a new water heater and to go back to the size we had would mean we would have to order it and then wait even longer for the darn thing to arrive. Honestly, boiling water and bathing from a bowl is no fun and so the smaller water heater made the most sense considering the circumstances. This one comment made me start to reflect on who I am to me, and who I am to my children.
The fact is I am also a positive person, but I find no fault in thinking "Gee that's a bummer, I hope we like having a smaller water heater then we had before." How do I explain to my daughter that there is a difference between being positive and being realistic? You can still be upbeat and positive and realize that something isn't quite the way you had hoped it would be. This is the second time in the last couple of weeks that one of my children has questioned my positivity which has me wondering…do my children know me at all or is there something to what they are saying?
I am not going to stop looking at things from every angle and if reality is that there is a fact to face, I think it best to face the fact. Being positive does not mean you walk around acting like Scarlet O'Hara saying "I'll think about that tomorrow" being positive means excepting where you are and looking at how to maintain it or get past it.
I hope that someday my children get to know the real me. I hope that they learn that who I have to be to them as their mom is not who I am to the rest of the world. I have to say being positive, that they will get to know the real me and that they will understand all I have done for them throughout their lives. However being realistic, I know that children (speaking from my own experience) only have realizations after they have children of their own, and sometimes (again my own experience) after the parent is gone. For the record, that's not being negative that's facing facts, which is also a good quality to have.