going to approach this slightly differently, but what other things are you doing? how busy are you?
I also don’t do much more than Wanikani at the moment, and that probably only around 1 hour a day. But I also walk the dog two to three times a day, work full time, go the gym three times a week, hang out with friends at least once a week, and spend time with my partner. Between all of that, there isn’t a whole lot of time to spend on studying.
So before beating yourself up over lack of motivation, maybe ask yourself whether it is maybe more related to a lack of time? And if it is lack of time you can reconsider what has more priority, learning grammar or the other things that you are spending time on. for me personally, all of the other things are important as well. So for now I am content with my hour of Wanikani a day.