There is nothing wrong with snap shooting, so long as you are able to come to full draw. Some people experience a problem snap shooting where they are compelled to release before coming to full draw, which is called target panic. Some of the best shots have been snap shooters, like Howard Hill.
If you want to think about the shot, it's best to do it close to a blank bale, so the result doesn't matter: you're just working on some aspect of your form.
When you shoot for accuracy, you should clear your mind of cognitive thoughts, and open your mind totally to awareness of what your body is doing. Cognitive thoughts are never about what is happening here and now. They are about the past or future or some conceptual place that is out of time entirely. They take away from your ability to experience the shot, which is what you need to do to be accurate.