I love this article by Marty Nemko, PhD. https://www.psychologytoday.com/blog/how-do-life/201705/developing-drive.

The biggest takeaway I found — and that clients seems to respond well to — is changing one’s idea of the pursuit of happiness. When you look at work as something negative or as a means for acquiring goods or allowing for leisure pursuits, then it’s hard to stay motivated. When one looks at productivity as a means to be happy then work begins to feel better, motivation to continue working is higher, and success can more easily be achieved.