How do emotions affect creatives? We have to be honest; the creative process is full of intense feelings.
It is a common problem. It could be personality, personal situation, or trust issues. Whatever the reason is, the problem is always the same: not everyone contributes with ideas when brainstorming. Even when it could sound like a huge issue and some difficult to solve, it's not. You just need to introduce one simple step in your creative sessions: first write, then share.