It isn't headmates or headspaces.
It's sorta along the lines of completely different mindsets/personalities I can slip into on demand. Not exactly pleasant to do a complete shift. Hence why the characters I normally rp as are somewhat similar to me in mindset.
It doesn't exactly hurt? It's more of how you would feel if you literally stopped being You and started being a Different You and both You and Different You were aware of it. And Different You knows You are the default so Different You lets You slide into primary after Different You is done.
inb4 someone brings up tulpas
Da fuck is that?
I think that's pretty normal then.
Also, Tulpas are imaginary friends for adults.