When I say that somebody is not letting me speak, it’s not that they’re really able to make me stop speaking, but they make it clear, over and over, that they’re not willing (or able) to hear what I have to say. That’s what I mean by “not being allowed to speak”. More precisely, it is a refusal to hear anything they don’t want to hear.
A person intent on not letting me speak constantly reframes the conversation, accuses, becomes indignant if I persist, insists on things that are often ridiculous and refuses to discuss the absurdity of their untenable claims. So I can, of course, speak as much as I want, even after the other person physically walks out of the room, hangs up the phone or cuts off communication, but “not letting me speak” is a way of saying someone is making it plain that they will never tune in to what I need them to hear.
Finding yourself in this situation, and feeling the human need to express what you are feeling, you may take up a musical instrument, begin to paint, become an interpretive dancer, master any one of a number of things including the art of writing clearly. This clear expression of the things you need to say that others in your life refuse to hear over time becomes a necessity, an important muscle that you exercise every single day.
In exercising this muscle you feel a certain mastery of things that are otherwise impossible to hold steady before you, the crucial things others refuse to let you say by refusing to hear you. I’d have to call this strong impulse to do something creative and soul-soothing to express what you need to put out there a major upside of being told to shut up by people who claim to love you.