Google's philosophy: it is worse to hire one bad engineer than to reject two good ones.
A false positive (bad hire) damages teams and is visible. A false negative (good candidate rejected) is invisible and costs nothing. Laszlo Bock admitted: "In our search for false positives, we have had a lot of false negatives."
This means you can do well and still be rejected. Don't take it personally. Many successful Googlers were rejected on their first attempt.