<human>: Can you succinctly summarize the text in 1-3 sentences?

My son is almost 5 and a few weeks ago he started a new behavior. I don't know why he's doing this or how to respond. I would love some insight or some response suggestions. 
He first states something he wants to do then says he's not going to do it. Then he talks and whines about it. He says "I really want to use that blanket but I'm not going to." He doesn't have a reason why not or else the reason is really flimsy. I let him know he can do or have it but he refuses. 
My working theory is that he's creating a safe place for him to experience "negative" emotions. There have been a lot of changes lately, all positive, but still stressful. I don't think he feels ok expressing his jealousy of his little sister or anxiety about school because he really loves both of those things. But you can love something and still have a lot of upset emotion about it.
By creating the trivial conflict he is creating a definable space to express himself. I'm not sure that's what it is but it's the only thing I can think of that fits. 
I've switched my responses to try to address his emotions in the moment. I give him words he can use to talk about his feelings but he hasn't responded much to that. I want to help him feel what he needs to feel then navigate his way out of the conflict. And I want him to stop the whining! I don't deal well with whining (although I'm sort of doing it now here myself).
<bot>: My son is creating impossible situations for himself. I'm not sure why he's doing this or how to respond to the whiny self-denial.