['Whenever I have to be assertive or confront someone, I get super nervous.', "I've had that feeling as well, especially if it is with someone that is close to me.  Is it because you dont like confrontation or a different reason?", "I think it's just sort of a social anxiety. It's gotten worse the older I get.", 'I used to have social anxiety as well.  I dont recall the names off the top of my head but some self help books with the topic have helped me in the past!', 'I think Im just worried about looking stupid and am afraid of rejection.']
I used to be that way too.  One thing to think about that might help is even if you do look stupid for a second nobody is going to remember 10 minutes from then.  Another thing that helped me was thinking about how good it felt if a stranger started talking with me in public for a 2-5 minute conversation and how it didnt upset me or make them look stupid so I shouldnt look stupid if I did the same thing.
I get really nervous when I have to confront someone and be assertive.