Are the following sentences gramatically correct?

"That night, despite the advice of his friend to stop overthinking about what happened last night, the ghosts and demons of his past intensified, until they became almost real. The nostalgia and melancholia overwhelmed him, causing his mental state to get even worse. That's why the next morning he walked to the closet and took an old metal box and carefully opened it. Tim placed a wooden amulet around his neck."