Have you ever tried working 2 - 3 jobs a day at 12 - 18 hours/day, sleep, eat and play aren't yet included? What kept you going?
Each one of us may had gone to the point of working 24 hours a day even without sleep to reach the needs we want for our families, putting food in the table, sheltering and clothing them warmly, and the comfort of having nice things for their convenience where in the back end it will yield the results or life we want for wife and kids.
Many people had their own reasons why they need to be a slave to their time in exchange for money. Three reasons I found in general is all about GIVING: