The sexuality teachings get all the attention, but I think the Church's teaching that stands most against the prevailing culture is that Fridays are a day reserved for fasting, prayer, and repentance.
In the US, Fridays are the day when people go out for lunch. After work, people head out to happy-hours with all you can eat buffets. People bring boxes of donuts to the office, and various celebrations are planned.
The Catholic who seriously makes Friday a day of fasting and prayer is probably capable of overcoming almost any temptation. I pray that I'll do a better job.