To be willfully aroused implies that there is the intent of becoming aroused before actually doing anything that leads to the arousal in the first place. God doesn’t expect you to be able to see the future and know beforehand that something arousing is about to take place and therefore flee or keep this from happening. He does however, expect you to behave in a chaste manner and not set out to become aroused. Temptations will inevitably arise but seeking them out is a sin, not being tempted in the first place. If you and your future spouse’s intentions are innocent in getting together: watch a movie, eat dinner, etc., then you can only do your best to avoid thinking inappropriate thoughts and avoid giving in to temptations as they arise but if you get together thinking “we’re going to make out and do some heavy petting tonight instead of having sex” then you should probably consider mentioning that in your next confession. Pray for God’s help and guidance and he will protect you from sin and temptation.
Peace
