Beware the Yetzer Hara's Approval

Powerful thought heard at a shiur:

The Gemara says that the way the yetzer hara works is today it tells you kach (such), and tomorrow it says kach, and then finally it tells you to serve idols. It's not that the yetzer hara starts off by telling you to sin, because you wouldn't listen to that.  The problem begins when you do a mitzva and the yetzer hara approves.

There are things that are “off limits” that you don't even consider doing.  Aveiros should be in this category, not in the category of I could do it, or not do it, because I have bechira (free choice), but I won't.  Likewise, mitzvos should be in the category of “must do,” not “it would be a good idea to do.” It should be non-negotiable, not open to discussion.

The yetzer hara, by giving approval to a mitzva as a good thing to do, not as something that must be done, makes inroads and opens the possibility of not doing it.  The yetzer hara makes it about you and your decision, as opposed to being about Hashem and your obligation.