I'm a little ambivalent about the idea of thinking positively. On one hand, I complain a lot. My boyfriend thinks I'm happy when I complain and while I'm not sure that's true, I admit I complain frequently. I knew a girl that was planning to go for a month without complaining because she thought it would change her life. That's just the sort of hokey crap that turns me off. (As a side note, I never got the follow-up story from her so I don't know if she succeeded). This person also believed in the law of attraction, and I just can't believe in that sort of thing, personally. I don't believe in the power of prayer or that the universe will grant a person what he or she wants just because of his or her thoughts. Actions matter. In my opinion, the concept is completely ludicrous and I'm always surprised when otherwise logical people live by it. This is why I've been wanting to read Barbara Ehrenreich's Bright-Sided ever since I saw her promoting the book on The Daily Show. From what I've seen and read, in the book she points out that thinking positively can lead to delusion and examines its effects on an individual and national level.
While I don't live by the idea that thoughts have the power to change your life, I do believe in making the best of a situation. Despite my complaining, I try to enjoy my life. I think the advantage of thinking positively is much more direct than the "power of attraction" suggests. On a basic level, if one goes into a situation with a good attitude, the pleasantries of the situation will be more evident. On the other hand, if one goes into a situation with a bad attitude, one will find things to be unhappy about. I know this from personal experience because I've definitely been guilty of it at various times in my life (I'm looking at you, teenage-Michael). A while back, I went through a period of depression, and it felt like even when I tried to be happy I couldn't. A friend told me I needed to fix my attitude, and while part of me resented the idea, he had a point. There's a Rilo Kiley song called "The Good That Won't Come Out" with the line, "You say I choose sadness/that it never once has chosen me/maybe you're right." This song was particularly meaningful for me during that period.
I have experienced many life changes since that period in my life: I have a better job, a great boyfriend, and I live in a neighborhood more suited to my lifestyle. I can largely thank these changes for the end of my depression. However, I still try to remember that line, and to remind myself that there is an upside to thinking positively. I do think it's possible, in a limited sense, to "create a beautiful day."