Didn't know you were a Heinlein fan shorty. I like you even more now. I think the man was psychic. Time Enough for Love is my favorite and there is more wisdom in the Excerts From the Notebook of Lazurus Long than most scholary screeds. Including my favorite and oft used here "Never try to teach a pig to sing, it wastes your time and annoys the pig". There is also great marital advice also i.e.; "Tell her she is beautiful everyday, especially if she is not"; "Rub her feet", just to name a couple.
I read his books in my teens and 20's, have re-read some since then.
This one I have to paraphrase because I can't quote exactly but really close and is included just to trigger archie:
Get one shot off fast, this will startle your opponent and give you time to make the second one count.