1. Our executive function!
(we cannot break down the mini-tasks involved in completing the task).
2. Past failures - What are you telling yourself about doing the thing?!
3. We are time blind! This means that we do not feel, see or experience time like neurotypicals do. When we have a task to do, especially when it's boring, we tend to think that the task will take longer than it actually does!
4. Perfectionism (and not knowing what the task will look like).
Want more? How To ADHD & Brendan Mahan also address' why tasks become so big in our minds with The Wall of Awful!
Why Is It So Hard to Do Something That Should Be Easy?
How to Do Something That Should Be Easy (But...Is...Not):
https://www.youtube.com/watch?v=hlObsAeFNVk