It’s hard to share your feelings in much detail with other people. We can all learn to use the same word ‘angry’ when a person has marked external symptoms of anger. But it’s hard for an angry person to tell you anything very nuanced about how exactly they feel.
A feeling, thinking about a feeling, and externalizing what you’re thinking about a feeling are all different things.
It’s “hard to think about the world inside our heads” but what’s especially difficult is externalizing what we’re thinking.
Our thoughts are precarious, indistinct, and extremely numerous. If there were a group of people capable of peering directly into our minds, we could hire them as our intracranial editors, and perhaps have several books published by lunch time.
But for now, we’re stuck with ourselves, trying to make sense of ourselves for ourselves and for others. We may not be infantile introspectors, but we’re all pretty awful at making what we think fit for consumption by others. We write to become less awful in this.