During one of my bible study teachings, I told my students that a ripe fruit can spoil If not harvested on time. I have walked past areas with mango trees where ripe mangoes fell off the mango tree and started rottening on the ground because no one harvested them on time.
If you understand this, then, just transfer that understanding to what happens when we don't win souls on time. Every lost soul represent the harvest Jesus was talking about in the opening text.
However, when they are not reached on time and won to the Lord, it may become impossible to reach them or even harder to reach because Satan would have indoctrinated them with his ideologies to the point where they become harmful.
For a clearer understanding, a terrorist was not born a terrorist. He was born in sin like every other person and for a time, his ideologies were normal and he had value for life until he met those who indoctrinated him with a more wicked ideology.
If such a person had been won to the Lord on time during the years when his ideologies were normal, he may not have become a terrorist. Also, that period of his life was the easiest time to reach him with the gospel. Now that he has become a terrorist, it is harder and dangerous to reach him. At this point, he is a decaying harvest.
Those we fail to reach on time may end up becoming our menace or the problem of our society. No prostitute was born as a prostitute. No armed robber nor ritual killer was born that way. Even children born by criminals did not become criminals immediately.
We failed to show them Jesus on time. Satan took advantage of our slowness and laxity, he reached them first and made them who they are today. They decayed.
Before they decay,let us reach them and indoctrinate them with the teachings of righteousness. That person you failed to preach to may become the pain in your neck tomorrow.
Don't waste time.