Lewis 9-11

Chapter IX
Why do our “trough periods” make us so vulnerable (43)?  Is this applicable to you?  
 When Screwtape talks about the troughs, I believe that he is talking about the times in our lives where we just stray away from God. Not always because we want to, but because we just forget to pursue Him. A person is always moving in their relationship with God. They're either going toward Him, or just slowly going backwards. These "backward" or "trough" times make us vulnerable because we forget and stray away from God and go towards our fleshly pleasures. This is majorly applicable to me because of the fact I can forget about God on a daily basis. I'm not trying to boast in my sinfulness, but I do boast on God's love for constantly loving me even though I forget about Him. I need to learn to just keep my head in check, and realize that I need Him.
What beautiful truth about pleasure does Screwtape share?  Make a list of pleasures.
God made "pleasure." It is not the demons or the devil who made the pleasure, but God. I believe, by what this is saying, that you can still grow in your relationship with "pleasure." That sounds contradictory at it's front, but there's something deeper. I believe it's the overcoming of that pleasure that bring you closer to God. When God gives you the strength to annihilate that pleasure then you rejoice in his strength and your weakness. 
I have many pleasures. Some of which are the pleasure...
1. To cheat in school.
2. To sleep in chapel.
3. To talk back to irritating teachers.
4. To be mean to irritating friends.
5. To swear.
There's many others, but I do have to learn from these and self-evaluate how I live.
Chapter X
What are your thoughts regarding “parallel lives” (51)?  What does this mean to you?
To me, "parallel lives" happen to most people sooner or later. Sometime in our life we get caught up in the wrong crowd and we tend to copy what they do so that "that crowd" will like us. This is not always a bad thing because sometimes people can get caught up with "good crowds" with "good habits."  More often than not, it doesn't happen this way. Most of the time people get caught up in the "cool/bad crowd" and they start to develop these bad habits with them. But, when the "cool/bad crowd" isn't around then it's easy to going back to a little "goodie goodie" around parents or maybe just other friends.
I can get caught up in this so much. Especially for me, I would say it's easier for me. Why? Because I'm an actor and so to copy other people habits or emotions can be a second nature for me. This is bad because I really have to go through my life and filter out what is bad. To even have a best friend accountable for how I live is helpful too.
Chapter XI
What are your thoughts on music and joy after reading this chapter?
Music and joy is as what I thought it was. Happy. Screwtape cannot stand music and joy because it "promotes charity, courage, contentment, and many other evils."