When it comes to embracing a mindset for achieving medium- to long-term goals, professionals don’t rely on motivation; they commit.
The chance that you will be sufficiently and consistently motivated at the same time as when you need to cook the nutritious meal, do that workout that you need but don’t like, get out the door when it’s dark and spitting fridge-temperature rain, or turn off the world at a decent hour is pretty slim.
If you find yourself struggling with consistency by relying on motivation, decide instead to commit to do the the work. Certainly leverage both intrinsic and extrinsic motivation when you have it, just don’t depend on it for your success.
There may be good reasons to not be able or want to commit to a current goal. It’s perfectly OK to adjust, postpone, or cancel a goal completely if the time is not right; just be transparent with yourself so you can best direct your (very) limited energy.
It’s also normal for unplanned rest days to sneak up–listen to your body and take them. But there’s a difference between needing to change the plan and not feeling like doing the plan.
Lastly, don’t forget to have as much fun as possible along the way; in fact I challenge you to commit to it.