I heard a quote
Never Do Yesterday What Should Be Done Tomorrow.
I assume that this means
Whatever you do, there will be tomorrow, so don't do it.
Am I right?
I see that it has come from a science fiction under the title 'By-Laws of Time'
Well, the perfect example I get in my mind for this quote is 'don't pluck a fruit off the branch before it is ripened'. Said that, you must do things when they are required. Doing those things much in advance makes no sense. Either your efforts will be waste or you may not get results.
This is actually a reversed version of the quote "Never do tomorrow what should be done today." The original quote was reversed for a movie about going back in time over and over again to fix what was messed up by originally going back in time to prevent a specific event from happening. The context it is used is to explain the plot of the movie. The other quote in the movie is "If at last you do succeed, never try again." and that is a reversed version of the quote "If at first you don't succeed, try again." This one explains why not to travel back on time to try and fix The event. It created a huge mess of time travel that actually made the situation worse.
I read it differently still. Think instead of the habits of human nature and our reluctance to stay in the now and instead ponder what could have and should have been with out lives as well as dreaming small and fragile into our possible futures.
You may wish that you had done a college degree, chosen a better career or travelled the world - when the "time was right" and so perpetually redo this in your mind (regret), when in fact, such things should be done tomorrow - i.e. imminently planned. Don't "do" and redo your yesterdays in your head - just do them tomorrow.
The reference, so far as I can tell without knowing your source, stems from Robert A. Heinlein's short story —All You Zombies—, a sci-fi magazine short he wrote in 1958. Wikipedia says that there was a film adaptation called Predestination, which is presumably what user Natman is referring to. I won't spoil the plot much, but the main character is part of the Time Corps that shows up in several Heinlein books. They have a bunch of slogans, all related to time travel. These include "A Stitch In Time Saves Nine Billion", "Never Do Yesterday What Should Be Done Tomorrow", "Even Jove Nods", and my favourite, "If At Last You Do Succeed, Never Try Again". The one you ask about is, obviously, a humourous reversion of Burr's original quote, and just refers to the prudent use or non-use of time travel. The slogans appear once more in the canon, in The Cat Who Walks Through Walls but in both they are minor details without an author-sanctioned interpretation. Like most cliché, really, real or fictional.