"What could you not accept...?"
The level of form is one great story; one tapestry of interconnection. Nothing at the level of form lives in isolation from the rest of the level of form. Everything that happens affects everything else. When something happens at the level of form there are multiple contributing factors. There are causes and effects and effects which became causes themselves all playing on each other. The attitudes, behaviors, choices, and energy of the self with which you identify all play into this one grand story. And everything else happening at the level of form plays into the self’s seemingly-singular little story within the grand story.
All of this happens apart from Truth (God). It is the opposite of Truth, so it is without meaning because Truth cannot have an opposite. Therefore it is an “illusion” or “dream”. Its interconnectedness is not the Oneness of Truth, Which is not made up of discrete parts joining, but is the same throughout.
When you (mind) change, the self’s attitudes, behavior, choices, and energy change, thereby affecting the self’s relationship to the rest of the universe of form. In response, the universe of form changes in relationship to the self. These changes of mind can be within the self’s thought system (personal thought system/ego). These would be changes of mind in the context of the self-as-reality. Or they can be caused by an awareness of Truth. These changes would be the process of self (form)-identification falling away.
So Truth never enters into form directly to change it. Your awareness of Truth indirectly has an effect on form. And this is, again, always without meaning in itself. Any meaning you see in it comes from you. And you only have two choices of perspective: the ego/personal thought system or the Holy Spirit, Which comes from your awareness of Truth.
“What could you not accept, if you but knew that everything that happens, all events, past, present and to come, are gently planned by One Whose only purpose is your good?” (W-135.18)
So this quote does not mean that the Holy Spirit goes out into the world and makes things happen “for your good”. The Holy Spirit’s “plan” is an interpretation. The Holy Spirit lovingly interprets what happens in the universe of form for the peace of your mind. The personal thought system in your mind may not like what happens in the universe of form. It may judge things as “wrong” or “bad”. But the Holy Spirit in your mind sees everything as a lesson. It will always interpret what happens in a way that leads to your lasting peace and happiness. And its interpretation will always make sense to you where you are right now.
Learn about the books The ACIM Mentor Articles, The Plain Language A Course in Miracles, 4 Habits for Inner Peace, and Releasing Guilt for Inner Peace at www.acimmentor.com.