Ah, to be a writer. I love when that first spark of inspiration hits you. How it can be a simple phrase, a facial expression, a place, a feeling, or a trait and from there the idea will spread out like oil on water. It gets bigger and bigger to the point where I must write it down to explore it more.
How the characters constantly surprise and delight me with their antics and personality; that's the rush of writing. The first time I tried to explain to someone how the character apparently was this or that, they stopped me and said, "You know you are creating the character, right?"
But it's not that simple. I may have started out with a few character traits but the characters are their own entities. They tell me who they are and where they are from, I have to honor who they are and don't misunderstand how they would react to things. Sometimes they take things in the opposite direction because of who they are but that's alright. I can only follow what their heart tells them what to do. At those moments, the writer must learn to adapt their story and trust that the character knows what they are doing. I love those adventures in their life.
May I always be surprised by my characters,
The dutiful writer.
I know what you mean, i find myself thinking about my characters throughout the day, and how i can be more descriptive about their personality by the actions they will do (if that makes sense lol).
The characters, for me, invade my mind at the oddest moments mainly they like to speak up just as I'm about to go to sleep. Hence, why it is handy to have pen and paper by the bedside. So yes, I understand what you mean.