I think the question is why do you feel you want to trim your hair ?
Then why do you question its effect on your beliefs ?
I think deep down you know the answer but want a majority view to say it is acceptable so that you won;t feel guilty.
Sorry if you find my response offensive, but when i think of all what sikhism stands for, how it came about and what people died for, this is a small sacrifice (its not even a sacrifice if you consider the reasons why we don't cut our hair).
It doesn't affect you as a person, you don't become a bad person, but you have to find the answer for yourself and be satisfied with your self. Its what in your heart that matters at the end of the day.