An earthen vessel, particularly in Bible times, was the least fancy and the least perfect, not polished or near perfection. Paul writes to the Corinthians that our imperfections are by design and are for the specific purpose of showing God’s greatness of power.
There is a certain level of comfort and safety in a trench. It’s not really the place you want to be, but you have some safety and comfort knowing you are protected. We have friends that are in trenches right next to us, so we all feel we understand what the other is going through. We see when there is a battle brewing, and sometimes we even hop into each other’s trenches! We know we’re on a level field of challenge, and being together helps us to get through the battle before us. We can’t be in the same trench and work against one another.