the #1 advice I would give to a young engineer entering their career is to do everything they can to avoid becoming cynical. technology has cycles, but it also moves forward. it's a helix. most people who churn through a few cycles end up becoming cynical, failing to see the orthogonal dimension of progress.
how to avoid cynicism? the primary way is to remove cynics from your life, and add optimists. second to that, keep working on new enough areas that you maintain a beginners mindset and can offset some of the pattern matching that leads one to thinking everything worthwhile has been done before.