As Avraham Avinu approached Mitzrayim the Torah writes he noticed Sarah's beauty. Until now, Rashi says, he never noticed her beauty, but as a result of an incident (Avraham saw her reflection in the water, as Medrash writes) he saw her. Was this because Sarah was a Tzanua? Rashi says it's not. Rather, it's because of the Tznius of BOTH OF THEM.
עד עכשיו לא הכיר בהמתוך צניעות שבשניהם"
(רש''י, בראשית יב :יא)
How many times did I tell myself if only women would dress more Tznius I wouldn't be drawn to look at them? If only I had the right filter on my computer, I wouldn't have a problem. Well, Sarah was absolutely Tzanuah, according to all standards, but that wasn't enough for Avraham to respect that Tznius. Avraham himself had to be Tzanuah too. A filter on Sarah was not enough; Avraham needed a filter on Avraham too. He knew that one cannot rely on everything around him changing and protecting him. Protection meant protecting himself from within.
Avraham's filter was on Avraham, in his mind and heart. As the recovery literature says, we need a "Psychic Change." That filter on the mind is a constant connection with HKB"H. He's the only reliable filter, and that filter is installed within us.
I've used every filter on my computer, and hoped for every filter on my surroundings. I've broken through them all. If I want to lust, there's nothing that can stop me. The only answer is to decide to be a Tzanuah myself, to install a filters on my hearts and mind, and that only HKB"H can do for me. May He give us all that gift soon!