I just don't get it.

Today my mother and I got into an arguement. It was over something so stupid! I have the responsiblity to the soccer team which  means I do scoreboard for the game and travel with them to the away games. BUT my mother doesn't seem to understand that I can't just drop that and do something else. Yesterday she told me not to make any plans because I had to drop my sister off for something softball. To ME, that's not quite fair. She knows I help with the soccer team and have since the begining. I understand family comes first, but it makes me feel awful that I am missing this soccer game when I promised. I guess we can agree to disagree about the situation.