They usually have a <u>limited level of awareness and emotional development</u>, no or little communicative intent, <u>lack of speech and serious motor difficulties</u>. The level of autonomy, if it exists, is very small.
Answer: If he's your friend then you should know who they truly are, and how to truly respond. So simply say, "You're not ready to go" Or "You're just not feeling it." Also depending on your reasoning for not wanting to go, I can't truly explain. But if you don't want to go, just because you don't want to go, It's easy as "Maybe next time" Or "Not today."