I'm glad Sivers focused on the positive, but our preferences don't only change to like more things. It would have been interesting to hear what Sivers used to love that he now hates.<p>In fact, I think we end up enjoying fewer things as we get older. After all, 90% of everything is crap[1], and decades of experience make us better at discerning quality. Also, the more memories we have, the less likely any new one will compare favorably to our best ones.<p>1. <a href="http://en.wikipedia.org/wiki/Sturgeon's_law" rel="nofollow">http://en.wikipedia.org/wiki/Sturgeon's_law</a>
This is what scientific/rational beliefs are all about, open to new data and susceptible to change. Normally, when your long held beliefs somehow become part of your identity, it becomes harder to let go off them when contradicting data arrives. Being ambivalent is also seen as a negative trait since it signifies indecisive mind. There are shit loads of behaviors and expectations that evolution has invented which not only are not relevant today but also harm the society and individual in the long run.
I'll back him up on the strength training -- you owe it to yourself to read Starting Strength. I read it at the beginning of this year and can definitively say it's changed my life.