"It is only with the heart that one can see rightly; what is essential is invisible to the eye." -Antoine de Saint-Exupery
What I think this quote means from the perspective of the main character in The Giver, Jonas.
Your heart is your guide. Full of power and strength, telling you what you should and shouldn't participate in. The cycle of figuring out what you should and shouldn't do, and then your heart buds in and pumps loudly, then telling you your decision, and what is right. Through your eyes it's nothing; a blank piece of page waiting to be written on. You stand silently for a long time, then shut you eyes and a huge wave crashes toward you. The wave is like glass, the little pieces cut your heart open and then tells you the truth. Finally, the bitter, sour taste in your mouth dissolves.