I have not always been as observant as I am now. In my twenties, as I was making the transition to a more frum life, Rosh ha-Shana and Yom Kippur were wrenching. I knew that I wanted to improve my observance of Shabbat and Kashrut, and there was a lot of change to be made. I could see the goal, and I could measure the distance, and although it was hard work, I could feel the effect it was having on me, and I could tell whether I was making the grade or not.
Now, the teshuvah process is much more difficult. I'm still falling short on my spiritual goals, but the shortfalls are harder to call out and address. I should be better about synagogue attendance (well, ok, so right now that one's taking care of itself, but when I'm done saying kaddish, how far will I backslide?). I should be better about guarding my tongue. And so on and so forth.
It's like clearing a rockslide. It's easy to find the large rocks, and though they may be heavy, you get a sense of accomplishment with each one you get out of the way --- by rolling, by lifting, it doesn't matter. Then you get to the pebbles and it gets starts to get tedious, but you know it needs to be done. And then you get to the sand and no matter how hard or often you sweep, there's still some left behind --- so you get discouraged and wonder what's the point; maybe you've done enough, so you stop for a while.
The Days of Awe come around, and you realize that there's more sand there than you thought, and you really should do something about it. So you resolve to get back to work on the sand.... but it's hard, hard work. Harder, ironically, than the heavy rocks, which required a different kind of strength.