Saying No

I used to wonder why women let so many unwanted sexual things happen to them when they could have stopped it by saying NO. Or yelling STOP. Or pushing him off. Or just saying ANYTHiNG , really. Then one day, it happened to me. It was someone I knew. And I was so disarmed, I thought the hand on my knee was safe , and I
Then it became more, and I let it happen without saying a word until I managed to get away somehow , and then I hated myself because I did exactly what I thought I would never let happen to me.
" it's all what a friend said to me one day "
The scary truth is , it's so hard to say no. Why are we taught so young that we shouldn't say no ? What is it that blinds us to the blaring red light telling us to say something? Is it the fear that we will be Embarassed shamed , kicked out......end up alone and why are we taught that submission is a prerequisite for security.