The storeroom principle is, you will only get out of storage what you put in storage. The principle hold true whether storing things in a toolbox, closet or the human heart. Whatever you do store will be available later, but what you don’t store won’t.
The acorn woodpecker earned its name because of its habit of making lines of holes in trees and storing an acorn in each one. Birders call this practice caching. Just like a squirrel storing up nuts for the winter, the acorn woodpecker will come back for them at a later time.
We humans are much more sophisticated and we have a multitude of different storage containers, for a wide variety of situations. But we might miss the applications of storage which we did not design and choose.
In Mathew 12:35 Jesus refers to a storeroom from which evil people draw evil and good people draw good. By looking at the verse before it, we can see this storeroom is a euphemism for the heart.
Brood of vipers! How can you speak good things when you are evil? For the mouth speaks from the overflow of the heart. A good man produces good things from his storeroom of good, and an evil man produces evil things from his storeroom of evil. Matthew 12:34-35 (HCSB)
The human heart is a storeroom, and when you store good things in your heart, then good things are what will come out of you later. But of course the opposite is true as well, if you store evil you will find your heart overflowing evil into your life.
When life shakes us up and something evil comes spilling out of us, quite often from out of our mouth, it’s because we are living out the storeroom principle. But it is possible to make some intentional choices earlier in the process, and by storing good things in your heart you guarantee good things will be what spills out.