Hashem Lets Go if We're Not Paying Attention to Him
I saw the following Ki Sisa thought in Nesivos Shalom:
How could Klal Yisroel, after all the Nissim of Yetzias Mitzraim and the revelation at Har Sinai, take such a fall as to worship an Eigel HaZahav? With all the justifications given by the Mefarshim, it's clear that it was still a seriously grave Aveirah.
If G-d would not help us defeat the Yetzer Hara we would never be able to do so on our own (Sukkah 52b). Only with Hashem's Shemira, His loving protection, can we even have a chance against the Yetzer Hara. What is this Shemira? Every day, a Bas Kol goes out from Har Sinai that says "Shuvu Banim" - come back to your Father (Chagiga 15a). That Bas Kol can be heard in our subconscious - the thoughts to return to Hashem, to do Teshuva, are that daily gift, they're the Shemira He gives us.
Hashem does not always provide that Shemira. He will lift His Shemira in two instances:
(1) If we're on a high level, able to defeat the Yetzer Hara without the help of Hashem's Shemira, He will remove that Shemira to create a real challenge for us. Kol HaGadol Mechaveiro Yitzro Gadul Haimenu (Sukkah 52a) - the greater level of spirituality you're on, the stronger the urge to go off course - because you've lost His Shemira (My understanding of this is that the Shemira is lifted in degrees - the greater you are the more Shemira is lifted).
(2) If we transgressed Aveiros that are insignificant and therefore we have no drive to do Teshuva, sometimes Hashem will lift His Shemira so we will transgress a greater Aveirah that would bother us enough to want to do Teshuva. Hashem wants a relationship with us and He'll let us fall in order to get our attention. (Wow!)
So when I conquer my Yetzer Hara, it's only because Hashem's Shemira helped me. And when I fall, it's because Hashem's Shemira was lifted and I was toast. Do I really think I'm in control? Did we think we were in control at Har Sinai, that we had the Yetzer Hara licked? Hashem is hugging me tight with His Shemira. He'll only let go if I'm not paying attention to Him. I just need to keep looking up to see Who's hugging me.
Sometimes I think the Nesivas Shalom wrote his sefer just for us GYE'rs.