This desire is my one true sacrifice to Hashem
We might have a tendency to think that after Rosh Hashana and Yom-Kippur when we worked so hard and achieved spiritual heights, the Yetzer Hara won't bother us for a while. But it is exactly the other way around. Precisely when there is so much spirituality and closeness to Hashem going on, the Yetzer Hara works over time.
Therefore, please dear Yidden. To make sure we don't lose all that was gained in the past month, we all need to be on the highest alert. After having been chased away during the Aseres Yemei Teshuvah, the Yetzer Hara comes back with a vengeance these days. There are many pressures now, work related, financial... we need to build a Sukkah, buy Arba Minim. It is easy to feel overwhelmed, anxious or stressed. And it is often these very emotions which trigger the addiction again. So we need to be on the highest alert and say to ourselves: "No matter how low or vulnerable I may feel now, physically OR spiritually, this is ONE DESIRE I have already decided that I am giving up to Hashem!"
Even if you find yourself slipping in other areas, such as eating too much, sleeping too much, lack of patience with the family, etc... and the Yetzer Hara says to you - "what's the use? You already lost that spiritual high from Yom-Kippur, give it up!" He'll do anything to make us fall into the addiction again, he'll make us feel spiritually low in other areas as well. But it is really THIS area that he wants us to fall in, more than anything else! Because he knows that if we fall here, he has us wrapped around his little finger.
So ignore the falls in other places for now. Stay committed to this one thing and shout in your heart, "I am NEVER going back there again! This desire is my one true sacrifice to Hashem!".
And if you overcome and chase him away, you will find that all the other areas you thought you were slipping in as well, were really no big deal. You will be able to quickly climb back up and will experience the true joy of the coming Yom-Tov!