One of these people (that might surprise you) is Arnold Schwarzenegger. There's a very nice speech of him on YouTube called "The 6 rules to success"[0]. I like to re-watch this speech every now and then and it helps keeping me motivated.
Bill Burr can explain very well why Arnold is such an inspiring person[1].
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I read books like "Drive, the surprising thruth about what motivates us" and many more, but it was not until I read "start with why" by Simon Sinek I understood my "why" and finally became truly internal motivated.
Now I am more motivated than I have time and energy, but luckily I also have a guidance tool that helps me put energy into stuff that fuels me more.
* Pick a specific goal that you care about. It can be as simple as I will lose 10 pounds or I will write software that parses a specific data format.
* Create some milestones. Maybe I can't lose 10 pounds all at once, but I bet I can lose 1 pound. Make sure that these are visible.
* Chart your progress, so you can see how your previous work got you closer to your goal. Review this chart regularly.
"Every step, a fucking adventure."