Do not be alarmed as this is nothing new. The Gospels read that if a man sees a woman with lust he's already committed adultery in his heart, so this thought bullshit is not new at all, just same old dogma modeled after our 'rules Book'.
The normal JW/person knows we cannot control thoughts, just like we cannot control dreams, etc. What we CAN control is not marinating/basking/caressing an inappropriate thought, for this is what leads to the 'act'.
No person can control thoughts that arise in the mind, it's part of our human imperfection. It's impossible and I'm sure God knows this too.
So, do not go too crazy about it.
DY