O: Once you knowJesus, and you decide to turn your back on him, you will be worse off than before.
A: Verse 18 mentions "those who have barely escaped," and it is talking about newfound Christians. If is a lot easier for those new to Christ to be turned back to their old ways of thinking by false teachers. I would think it would be more difficult to pull an older Christian back to their previous ways because of the amount of time they have spent with The Lord. And I believe it is the job of older Christians (and by old, I do not mean age, but how long you have been with Jesus) to watch out for the newer Christians and help them on their path. They need guidance so they do not fall again.
I have read once that it is easy to pull one person off of a table, but if there are two people on a table, they can stand firm against the one pulling them down. We need to be the second person on the table for our brothers and sisters so they don't turn away from Christ. We need to help them see the greatness of his glory, and that his glory continues and never fails. If they fall away from Christ again, it will be harder to get them back. It is our job to keep them from falling.
P: Lord, I know you want to use us to help our brothers and sisters in Christ from falling away from you. Please give me the courage to take on this task. Thank you for giving my fellow Christians the courage for the same task when I was new. Without them, I may be lost. Please give me the strength to continue to stand up for them. Amen.