It was necessary for us to call the on-call nurse in to take her place because otherwise there wouldn't be enough staff. This nurse had to come in and work because the other nurse wasn't going to be on the clock.
We never have to fear a time when our Lord is not "on the clock." He is always working for us, in us and through us. He is always working in our lives. He is the Author and Finisher and the Alpha and Omega. There will never be a time when we are disappointed with His work ethic or with His attendance record.
"O taste and see that the Lord is good: blessed is the man that trusteth in Him. O fear the Lord, ye His saints: for there is no want to them that fear Him." (Psalm 34:8,9.)