What does "time and tide wait for no man" mean?

One must not procrastinate or delay, as in Let's get on with the voting; time and tide won't wait, you know. This proverbial phrase, alluding to the fact that human events or concerns cannot stop the passage of time or the movement of the tides, first appeared about 1395 in Chaucer's Prologue to the Clerk's Tale. The alliterative beginning, time and tide, was repeated in various contexts over the years but today survives only in the proverb, which is often shortened (as above).