Nobody here is telling you to work harder
Read the room and the advice is almost entirely about the first five minutes. Ziglar attacks preparation, Twain attacks delay, Levenson attacks measuring the distance, Rohn explains why the enthusiasm that got you out of bed will not last until Wednesday. It is a fair diagnosis. Very few weeks are ruined by insufficient effort in the middle. They are ruined at the beginning, by a start that keeps being postponed until the week is too far gone to rescue.
Franklin twice, and a subject that did not exist until recently
Benjamin Franklin has two of these fifteen lines, from 1746 and 1747, and everything else is modern. That gap is the whole story of the room. Monday is not an ancient complaint; it requires a five-day week, which arrived in the 1920s and became general after the Second World War. What Franklin wrote was about time in general. The room around it was built by a calendar that did not exist when he was writing.
What is a good Monday motivation quote?
Arthur Ashe’s “start where you are, use what you have, do what you can” — because it removes the three conditions people most often wait for. Ashe learnt tennis on segregated public courts and won Wimbledon, so it is a description of what he did.
Did Mark Twain say “the secret of getting ahead is getting started”?
It is credited to him nearly everywhere and cannot be traced to anything he wrote or said, so it is labelled attributed here.