Yes. I've never read it or whatever (I guess there is a book) but I know the theory and I definitely agree. That's why it is so important to limit our negative influences and make friends that we would aspire to be more like.
I don't think it's a literal as The Secret, but I think in general, when you think positive, positive things tend to show up. Maybe it's a matter of focus - you see what you expect to see. And if you are pessimistic, you probably see the bad easier, and miss the good. And when you are optimistic, you see the good, and don't see the bad as well. <br />
But what do I know? I'm blonde. <br />
At least we know you have more fun! ;-)
And of course, you know the secret - that I am not a real blonde, so I get to have brains too. I just disguise then with my blondness.
Of course you can " make your own happiness " its a choice. But as far as that book goes..nope a bunch of new age thought.