The book contains a glossary which in turn contains the following entry:
causality (also know as cause and effect). Everything that happens to us is the result of what we have thought, said, or done. What we undergo in this lifetime are the consequences of what we had done in our previous lifetimes, while what we do now will determine what we undergo in our future lifetimes.
I don’t know where the second sentence, “We alone are responsible for our lives,” comes from. It’s a common expression found in many places. I assume that someone cobbled together two separate quotes, or perhaps simply made up the last part, and it’s just coincidence that it was a preexisting saying. After all, you can find that expression here, here, here, and here. These each appear to be independent, and yet identical, statements.
Now it’s not uncommon to hear Buddhists to say that everything that happens to us is the result of our previous actions (karma). But that’s not what the early Buddhist scriptures teach. In fact that view is one that the Buddha argued against, for example by saying “it’s not proper for you to assert that, “Whatever a person experiences — pleasure, pain, or neither pleasure nor pain — all is caused by what was done in the past.”‘
Some Buddhists get very angry and call me names when I tell them that the Buddha, from what we can tell, argued against the idea that everything that happens to us is the result of karma. Presumably their own teachers say otherwise, or for some other reason they hold to that idea strongly. The other way to be unpopular with Buddhists is to say you’re agnostic about rebirth. It’s notable that the things Buddhists most readily get annoyed about are things they can’t verify in their own experience.
One problem with this notion of karma controlling everything is that it tends to lead to a blame the victim mentality. People I know who have been to see certain Tibetan teachers espousing this view have asked if, say, the Jews who were annihilated in the Holocaust supposedly deserved their fate, and the answer has been “Yes.” That horrifies me.