To be free, is it to say no ?

Hi
According to me, "To say no" mean refusing what the other one proposes us, imposes us or oppose us to another will than his.
To say no is to express a personal feeling, can be seen as an existentialist assertion : if I oppose to others it's because I possess my own individuality.
For Sartre, the man is a choice.
For Kant " the freedom is a property of the will of all the reasonable beings ".
So when I oppose to another will, Can't I assert that I am free by expressing my will?
The freedom proves to itself by coming true, when the man realizes his personality through the events of the world, instead of undergoing them from the outside.

And yours, what's your opinions ?
Criticize my point of view and argue please