Family Relationships

I have a lot of patience with a lot of people. Why does that patience not carry over to my relationship with my mother (who does NOT know about my blog, nor could she ever figure out how to find it, since she won't touch a computer)? I find myself constantly exasperated with her. Those faults I can accept and tolerate in others just don't cut it when it comes to my mom. I find it so frustrating to talk to her. I am not sure if it is because I am so comfortable with her I am able to let go and not worry about her getting mad at me or if it is just a family thing. I regret that I am often so short with my mother, I wish we were closer, but it doesn't seem meant to be. I wish I knew how to have the patience with her that I do with so many others...