Motivation is weather. Some days it rains. Choosing to go anyway is the umbrella.

Feeling like it is not a prerequisite, though it is easy to run a whole life as if it were. Motivation shows up unevenly and for reasons that have little to do with what you are trying to build, so anything dependent on it will be built unevenly too. What holds is the arrangement you make for the days it does not arrive.

Decide now what the bad-weather version looks like, the shortest session you would still count. Do that on the next unmotivated day and let it count fully.