When you think you’re tougher than tough and you know you won’t slip into sin is exactly the time when you can fall. The only way to prevent that fall is to stay close to God. Read I Corinthians 10:12-13. (click on link below and read verses 12 and 13).
http://bibleresources.bible.com/passagesearchresults2.php?passage1=1+Corinthians+10&book_id=53&version1=51&tp=16&c=10