Listener question : speaking up

When I want to speak up for something I want in front of others e.g asking a builder to change something when he is halfway through a job because I was either : misinformed, I realise there is a better option OR I just don’t like something. 
How do I navigate this communication cleanly and respectfully (for self and other) when i'm silenced by my freeze, fight or flight the situation. I get flooded with feelings of shame, self-apology and am scared of being seen as a hassle. Perhaps i would aks for the change and then still feel the same because of course it's nothing to do with them is it.

I suddenly lose clarity about what I want or what is right and if I'm just be reacting to a trauma of past feelings of powerlessness, fear of being misinformed and fear of having been silenced.  What is the opportunity for me to see here and how do i not make ALL of it feel wrong