Like the Aron, our Neshama also has multiple layers.
Gold cannot decay and will not tarnish. It is pure and will always be beautiful. Wood on the other hand is subject to decay. It can be beautiful and polished but it can also be rotten.
The inner core essence of every soul is pure gold. It desires only goodness and connection with Hashem.
The middle layer is our psyche of feelings and ideas. Here we have the emotions and understandings of our G-dly soul, but we also have the desires and dark emotions of our animalistic side. We cannot stop ourselves from having these feelings. Like wood, our middle layer can be beautiful but it can also be downright rotten.
Our outer layer are our behaviours; our thoughts, our speech and our actions. Tanya teaches that no matter what we may feel on the inside, we have the ability to rule over our negative inner feelings to not give them expression.
So while the middle box may be a place of inner turmoil. Our outer box, our behaviours can and should still be like pure gold.
Through this, we too become a fitting vessel for Hashem’s presence to rest and be manifest.