I find it impossible to openly express to anyone, even close friends or family members. Actually especially family members.
I used to see a counselor to help me with some issues I was having with life, after about a year of me not being able to tell her anything she finally gave up on me.
Every time she asked me a question, I'd dance around how I really felt by telling her facts surrounding it, then when she would actually ask how I felt, my mind would lock up while I was thinking of the words to describe it.
There is an exception, when I am going through particularly tough times, and a close friend actually prods me to talk about it, they absolutely have to do it over some instant messaging program. As mentioned above if asked in person my mind seems to lock up... but typing it out doesn't seem to have the same affect.