The very fact that these people post openly on the internet and share their problems with impurity is in itself your answer, Spouse.
A firm resolution not to sin again must include a resolution to AVOID the occasions of sin. Now, we know that impurity appeals directly to the senses, through sight, hearing, etc, and through the imagination. Therefore, posting about one's own fantasies (even if they are temptations and unwanted) and reading others, about impurity, is surely putting oneself in the near occasion of sin. I suspect this is why these people are not able to resist temptations. They are putting themselves directly in harm's way by dwelling on these incidents and thoughts. They have to be thinking about them in order to post about them! These matters should be kept private between one's confessor and/or spiritual director, not plastered all over the internet. Perhaps they do not realize it, but it is surely adding to the problem.
The Sacraments are wonderfully efficacious if we comply with God's grace. But it would be stupid if, for example, an alcoholic prayed to give up drink and then went to the pub with his friends as normal, expecting God to "fix" the problem when he is clearly not avoiding temptation. The same thing happens when we dwell on impurities, we are like the man deliberately going to the tavern and expecting God to stop him drinking.