As a boy, I remember going to a movie theater with my family and having an usher look at our tickets and guide us to our seats using his little flashlight. His job was also to ask noisy patrons to be quiet, help clean up spilled soda, and serve families in any way necessary so that all could enjoy the film.
As a parent, my job is similar to being an usher. In responding to my children, I want to guide them to their work using a "flashlight" of truth.
"You're _______ [tired, hungry, overwhelmed...etc.]. I'm sorry about that. God has said that He will help us in the midst of our troubles (Psalm 46:1). Here, let me help you get started on your homework. Let's pray first and ask God to help you."
Then you minimize the noisy distractions, help them clean up the “messes” they've made from sloppy thinking or sloppy work, and serve them in whatever way is necessary to help them accomplish their task.
In short, we need to be the "objective" reality to our children that brings truth to them from the outside. They are caught up in their FEELINGS about their work, their friendships, and their world and need to hear truth. Not our good advice... but truth. God has given us a whole book of truth so as to be able to live in this world in right ways.