Here's the rabbit trail. What does it mean to "believe something in your heart"? Are you supposed to have some sort of feeling associated with that particular belief in order to authenticate the belief?
Here's a for instance. At Artisan we often use a creed as a confession of what we believe. I would say that at a very base level, I believe those things that you find in a creed. But I don't necessarily feel any connection to it (my beliefs) beyond a sort of academic level, or I just notice that I feel kind of dissociated.
Likewise, I feel sort of dissociated from much of life these days. Almost, but not quite, fully numb. Not quite because I do still feel anger very well. But other than feeling anger, I feel separate from everything else. This is not for lack of things around me that I could feel good about. It's more that I am kind of an observer to those things rather than a participant in them.