Autism

I partly agree and disagree with the description of executive dysfunction. I would also break it into two categories, but the first encompasses both aspects of the description by "overwhelmed".

In this case, the anxiety or stress that impedes function is due to uncertainty around how to achieve the desired outcome. The degree of anxiety or stress is dependent on the cost of failure; e.g. something with no perceived stakes (or very low stakes) allows for a high degree of uncertainty and an imperfect or incomplete plan can be executed because the cost of it going wrong is negligible. However, as the stakes rise, the degree of uncertainty required to create a "barrier to entry" (i.e. a sufficient amount of anxiety or stress to prevent action) decreases. The uncertainty itself could simply be not knowing how to approach or break down a task as per the comment, but it is also often the uncertainty introduced by other people. If you know someone well, then you can have reasonable confidence in how they might respond to a particular topic. If not, though, and they are a key part of achieving said goal, then oh boy does that cause stress!

The other category is not directly due to anxiety/stress but instead a result of fatigue, burnout or being overwhelmed (i.e. near meltdown). The brain effectively goes "nope" and refuses to process the required information no matter how much you want it to or how important it is. The irony is that if the anxiety or stress from the previous category is high enough, it can actually create this overwhelmed state, but in my experience severe fatigue, too much sensory input or too many cognitive demands (i.e. being forced to juggle too many tasks/problems/interactions at once) will readily create this situation too.