Well, other than the generic "work hard, and be honest" stuff that my parents, particularly my father passed along (yes, it was true and I did very well by it),
one of my favorite pieces of advice is from JP Morgan (the financier, not the bank) "Think a lot, say a little, *write nothing*"
Also, all of the advice about one-itis I've read over the years really is gold. It's amazing how it frees you up when there is more than one romantic "possibility" in one's life.