In my opinion, you have to “feel it” in order to do your best work.
However(!), and also in my opinion, you shouldn’t always strive to be in a position where you “feel it”. While it is important to spend most of one’s life feeling it / doing their best work in order to be fulfilled, the hazard of insatiably “feeling it” is that you can much more quickly burn out.
Working with passion fuels a level of intensity and emotional involvement that can take a while to recover from if you don’t get the result (read: success) you desired.
But yes, you do indeed mostly have to feel it.