Dare to not feel guilty

Sometimes I feel that me and my Mom talk different languages. We are talking to each other, we use very calm intonations - but I just know sometimes that she doesn't agree with me, or that she is a bit disappointed because that is not exactly what she wants to hear. And after such talks (especially when it happens over the phone) I always feel guilty. Guilty that I've made my Mom upset. And here comes the question - what do you think is better - to be loud and argue when someone doesn't understand what you are trying to communicate, or to talk quetily, try to be respective of each other and not hurt each other and for those reasons not be able to say everything that's on your mind? I think that neither of them are good, but sometimes I wish I was brought up in a family where you could argue to defend your opinion. We never argued in my family. I think it is very good, but that has also influenced me - for a long time I have been afraid of expressing my real thoughts, because I didn't want to provoke an arguement. And now when I try to be more honest about my own thoughts and ideas, my Mom is still not ready to put forward her ideas. If I try to explain that I am right, she wouldn't tell me different, she would just say "OK" and I would know that she doesn't agree and that she is upset about it. But in order to keep the peace, she will not argue with me. But that's what makes me feel guilty - the feeling that I have proved my own Mother wrong. And this is what I am working on - it is not myself that she feels this or that way. I only say my opinion, how to react this opinion is her choice only and I cannot influence that. 
So the advice of the day is (it's mostly for myself): dare to not feel guilty.