My SLP explained that stuttering, especially bad blocks can trigger our flight, fight or freeze response. Our conscious thought processes take a back seat while our body tries to react to what it perceives as a threat, so it's no wonder we lose track of our thought process during these blocks. The only way we've talked about moving past this is exposure therapy and having lots of practice in these situations, training our body that these situations are actually safe. You need to pick and choose your battles though and practice in low stress situations repeatedly.