As we all know, Shemiras Shabbos was THE main Nisayon during the first half of the 20th Century. The six (or seven) day workweek made keeping Shabbos extremely difficult, and, at the time, there seemed to be no light at the end of the tunnel. Even those who were able to pass the Nisayon must have wondered whether the next generation would be able to hold out.
The five-day workweek changed everything. All of a sudden, keeping Shabbos no longer conflicted with earning a living! Those who had passed the Nisayon of Shabbos now had children who were trained to keep Shabbos, with no great Nisayon to desecrate it. However, those who did not pass the Nisayon of Shabbos when things were difficult (and we're certainly in no position to judge them) wound up with children and grandchildren who, for the most part, are non-observant, even though the Nisayon is gone.
I mentioned this thought to the Rosh Yeshiva, Rav Aharon Feldman Shlita recently, and he pointed out that women covering their hair used to be a tremendous Nisayon as well. What happened that the Nisayon went away? The Ribbono Shel Olam works in amazing ways! When Kennedy was President, the First Lady once wore a wig. All of a sudden, wigs became in style, and the Nisayon was gone!
The same is true with our Nisayon. It seems that there's no way out this time! What will be with our children and grandchildren? But it's not true. Every generation has its own Nisyonos. As the Sar shel Eisav asked Yaakov Avinu: "Lama Zeh Tishal Lishmi" - "Why are you asking my name?" Explains Rav Chaim Dov Keller: The Sar shel Eisav, who represented the yetzer horah, was saying: "You want to know how I operate? There's no set way. It's different in every generation. In one generation the Nisayon will be Shemiras Shabbos or women covering their hair, and in another generation, the Nisayon will be the Internet."
Let's learn a lesson from the generation that was Moser Nefesh for Shemiras Shabbos. Their children had the Nisayon removed from them, even though it seemed impossible. The same is true if we are, b'Ezras Hashem, successful with our Nisayon, whatever it takes to accomplish that. We don't want to be in a position, chas v'Shalom, where our children and grandchildren continue to be Nichshal, even when this Nisayon, b'Ezras Hashem, is taken away (perhaps with the help of GYE :-)!