I just thought I'd share some thoughts about my own experience with this. While in college I have found it interesting to see the parallels between struggling to grow as a musician, especially as a vocalist, and struggling to grow in holiness. Being a musician has helped me to better understand the struggles of the spiritual life. As a musician, it can be frustrating at times to see how slowly you progress. You realize you have deeply engrained habits in the way you sing (or play), that are very difficult to change to become better. To improve, you must be diligent in working on those problems/habits specifically even if you would rather practice what you are good at. You also will only improve as much as the effort you make to practice. Your singing is also very much affected by how well you physically, emotionally, and psychologically take care of yourself. For example, if you deprive yourself of sleep, it is very hard to sing without going flat, or to truly focus during practice time.
How similar the spiritual life is to musicianship! We tend to have deeply engrained sinful habits that can be frustrating because it is so hard to root them out. We can also become frustrated with ourselves when we know we do not take the time or effort to practice those virtues that will counter and help to change such habits. We also tend to prefer to continue those spiritual practices that we know we are good at and not challenge ourselves to take a step deeper in transformation and the path to holiness. We get in a comfort zone and for a while often like being in auto pilot. Our prayer life is also affected by every other aspect of our well being. If I am lacking in sleep, going to adoration is not as fruitful because I cannot focus and be as attentive to the Lord.
No matter what aspect of my life, it seems I cannot escape such fundamental spiritual realities. It manifests itself in all tasks and vocations in life. And on that note, I am going to head off to go practice organ, since I desperately need to if i really am going to get any better in that!