After John records the end of v.3 in John 21, it’s apparent that the disciples’ overnight fishing efforts were completely fruitless. This fishing expedition serves as a final lesson from Christ, teaching them what they can accomplish on their own. When worded like that, how can we not think of Jesus’ previous teaching in John 15:4 Abide in Me, and I in you. As the branch cannot bear fruit of itself unless it abides in the vine, so neither can you unless you abide in Me. 5 I am the vine, you are the branches; he who abides in Me and I in him, he bears much fruit, for apart from Me you can do nothing.
It’s been mentioned before, but it bears worth repeating, that the nothing in that verse does not necessarily indicate a lack of activity. There are many things being done, even in the name of Christ, that are void of Christ’s power and influence. Jesus is teaching that all our lives must be characterized by an entrustment of ourselves to his word and his life-giving power.
On the other hand, what the disciples accomplish in their night of fishing is what can be expected when we do life in our own strength, with our own understanding, while pursuing our own desires.