Have you ever used the words "I'm Spent" at the end of a long hard day? Have you gotten to the end of a task, or maybe finished a particular month and plopped in a chair or let out a sigh saying "man I'm glad that is over"? We all have, but what's really being communicated is that we have nothing left to give, we are done, exhausted, and in reality we have an empty tank.
When you spend yourself on a daily basis getting nothing in return constantly pouring out you're giving out of a deficit. When you invest yourself into what you do and into others with a healthy ROI you see fruit and fulfillment in your giving and you are giving from a surplus.
"God is our refuge and strength [mighty and impenetrable], A very present and well-proved help in trouble.” Psalms 46:1 AMP
