I think motivation is a constant hum in the background, a white noise.
Sure, it’s okay to seek overt, external motivation (and get it) in the early days of your fitness journey < barf word. After that wears off, look at the big picture and motivation becomes easy:
I don’t want to be fat. I don’t want to die young of some easily preventable disease. I don’t want to be on 15 prescription drugs by age 55. I don’t want to deal with smug doctors. I don’t want to lose the ability to get an erection. I don’t want to be nonfunctional and weak in a real life situation. I don’t want to be a victim or a soft target. I don’t want to look my age. I want to be pretty!
Call it negative motivation: get motivated by being scared of something. Fear of being fat/weak/sick, etc. Fear is fuel. Not the cheeriest way to get and stay motivated, but it’s been working for me for decades.
Kinda related to the whole promotional vs. preventional motivation thing.