We read in this week's Parsha (Eikev):
"If you should say in your heart that the nations (read: Yetzer Hara) are much greater and stronger than us","EICHA UCHAL LEHORISHAM - how can we conquer them?".
Notice that the Pasuk uses the word "Eicha", like the first word of "Megillas Eicha". Perhaps this is a hint that when we ask this question and we don't believe in the power of Hashem to save us, we bring upon ourselves all the Churbonos! The Zohar says that the root of the churbon in Megillas Eicha comes from the original "Ayeka - where are you?" that Hashem asked Adam after he ate from the Eitz hada'as. ("Ayeka" is spelled the same as "Eicha")...
And what does Hashem answer in this week's Parsha? "Do not fear them, remember what Hashem your G-d did to Pharaoh and all of Mitzrayim.... that Hashem took you out with great wonders, etc... So Hashem will do to all the nations that you fear before them.... Do not fear them, for Hashem your G-d is within you, a great and awesome G-d!"
Yes, the Yetzer Hara is INDEED MUCH stronger than us, but he isn't stronger than HASHEM!! And Hashem is not asking us to conquer the Yetzer Hara. He knows that we can't do that alone. All he's asking is that we put our trust in HIM to conquer the Yetzer Hara for us. "Hashem your G-d is within you, a great and awesome G-d!"