I find this advice to be right on the spot. However, feeling demotivated at work usually spreads to another areas, and it's hard to be motivated on something else for a long period of time.

In order to fix that I think the advice of "discipline" as mentioned in another comment below, is key.

I have so many goals on so many topics that I can't work on all of them every day. However, I started with one (exercise), and worked to be disciplined on that one, dedicating 1 1/2 hours, 6 days a week. I also added meditation (I practice buddhism) for 1/2 hour every day, where I clear my mind and focus on all of my goals.

After consolidating exercise and meditation, and feeling that it was already part of my routine, I added a second goal (studying). All of this while having a 9 to 5 day job, remember. I leveraged on apps for reminders, and habit trackers so I try not to "break the chain".

I went from being quite unmotivated, to being motivated on different areas, and that pushed me to find ways to be motivated at work.

Discipline goes a long way.