Most of us know what you're refering to. At first a now-frum friend of mine, said he stopped doing a particular sin 2 years ago, I said that it was impossible and (like Sarah-rishon) I laughed.

That was last year, now (working hard to be a ba'al teshuvah) I have not done a particular sin in a year.

I thought it was impossible. For the first few months, I failed a couple times. Later, it became easier, but then suddenly much more difficult, but now, a year later I'm cured of that sin.

It'll always linger in your mind, but you'll have the strength to stop, eventually, just gotta make that first impossible step like Moshe at the Sea of Reeds.

As Dov Ber of Mezrich said, "it can be a life time struggle (speaking about arrogance)," but that is the essence of teshuvah.

So just go and do it.