It has done something else that is most unexpected. It's made my writing easier. Every move and reaction and interaction flows smoother and more true to the character. There's no more guess work. The characters are dictating the pace, the moves, and the direction of the action, development and overall journey.
So how do we shape and sharpen our characters? Here are a few suggestions I've gleaned or learned for myself on tightening the loose ends of your characters.
1. Try finding a picture of your character(s). A critique partner of mine checks out modeling websites and any thing else she can find until she's pinpointed the perfect physical persona for her characters. Then she describes them ... the tilt of the chin, the shade of their eyes when they're upset, the tightening of their face when they're concerned, etc. So much can be brought to the surface and carved out by doing this.
2. Ask a few questions. I borrowed these from Larry Brooks:
What is your core need? (And what happens when that need is not met?)
What is your greatest fear?
What is the incident that wounded you early in your life, that got you believing a lie? (and what is that lie?)
What suggestions do you have? What works for you?