When you're working on a big project that's going to take multiple sessions, it might feel intuitive to work until you aren't enjoying it anymore. You might be better off, however, stopping right when you're starting to have fun.
Photo by Cas
If you stop right when the excitement and fun start to kick in, you leave yourself something to look forward to during the next round of work. Jeff Haden at Inc. explains why this is one of the best motivational tricks:
Stopping in the middle of doing something awesome -- or stopping right before you'll start doing something awesome -- ensures you'll avoid the temptation of procrastination. Stopping short ensures you'll ignore all the enticing distractions that inevitably pop up when your motivation has flagged. Stopping short allows you to instantly focus and concentrate when you pick back up whatever you were doing. You won't be able to help but dive right in because you'll be too excited -- and that initial enthusiasm will positively affect the rest of your day.
You'll be less inclined to get started again if you can only think of the fun parts you've already done. Start with the fun stuff and end with the excitement of fun stuff ahead.