When I'm in an "down" period, and I know that I am having a yerida, , I wonder how I can muster the motivation to pass the multitude of tests and temptations each day, starting with getting up when my alarm clock goes off, so that I can learn before davening.
In parshas Va'era, the Meor Einayim says that every person is tested, just like Avraham Avinu was tested with 10 tests. And what is a test? He says that it is when Hashem removes from you your feeling of connectedness from Hashem through Daas, and then puts you through the nisayon. At that point when your feeling of spirituality and connectedness (hiskashrus) is gone, all you have left is your bechira, your free choice.
If Hashem left your with your feeling of connectedness, then certainly you would remain holding on to your path. Through this process of taking away your feeling of hiskashrus, Hashem limits your Daas (though not taking it away completely) and if you remain commited and pass the test, it is because you fixed the Daas (conciousness of Hashem's presence and Hashgacha at every moment) into your heart when you were in your "up" time, your time of hiskashrus.
This made me think of what I posted here a week or two ago, when I said that Reb Tzadok taught that your measured not by how great your highs are, but by how great you are on your "lows." The higher you can remain during your low times, the more it is revealed how much you've actually acquired your madreiga.