Maturity is marked by our ability to think OUT. How far outside of yourself can you comprehend? Can you grasp the reality of a thousand people with intricate stories and personalities? Can you comprehend the idea of 100 years from now?
On the other hand, immaturity is proven by self-focus. This can be seen in impatience, a lack of empathy for others, and an inability to grasp the big picture. Just think about it! How far OUT can a toddler understand? They don't even know that TOMORROW exists! The older we become, the more we can understand the concept of that which is outside of ourselves.
This is just another reason why we can fully trust our Lord, who is infinately mature and capable of thinking OUT. He sees how billions of lives and stories can intertwine, and he understands the centuries it takes for a plan to unfold. So trust Him friend, trust Him.