John 21:15 Simon, son of Jonas, lovest thou me more than these?
The apostle Peter was known for “putting his foot in his mouth” as the old expression says. Peter told the Lord he could always count on him, even when others would fail Him. However, a short time after that promise Peter denied his Lord three times . In the final denial he even cursed to demonstrate he was not a follower of Jesus Christ. He then went out and wept bitterly. From the human point of view that would finish the ministry of Peter. However, not much later Peter stood and preached on the Day of Pentecost (Acts 2) and 3,000 people were saved and baptized in one day.
What does that teach us? First of all we serve a God who will forgive even when our sin is grievous. There can be profitable service after failure if we get our heart right with God and allow Him to use us once again. Do not let the Enemy discourage us. Let us serve the God of the second chance.