""Never get invested emotionally.""

Second this, because it so hard. You pour yourself into something, and then management changes, direction changes, and suddenly your baby turns into crap. Your creation probably isn't even put out of its misery, it is allowed to live, but gets tortured, and mangled into some unholy abomination.

It can be very upsetting. I still dwell on a big project, get angry, tense, it is very unhealthy, and also difficult to let go.