Here and here are two great articles by Randy Alcorn on sexual temptation. An excerpt from the first article is below. These are really worth reading.
What level of pride is required to believe that sexual sin could overtake Samson, David ("a man after God's own heart"), Solomon, and a host of modern Christian leaders, but not me? Paul's warning in 1 Corinthians 10 deserves a prominent place on our dashboards, desks, or Day-Timers: "If you think you are standing firm, be careful that you don't fall."