If your practice isn't "sticking", maybe you aren't doing enough "reps". Many people will take my advice on working in small sections, but won't repeat enough. They'll figure out how to get through a section, repeat it maybe once, and then move on. But really, they ought to play it through several more times. These "reps" are where the real muscle gets built. Don't spend several minutes figuring out how something goes without repeating it. If you do that you are wasted most of your time!
Alternately, if you're moving at a glacial pace, learning a measure a week or something like that, maybe you are doing too many reps. Its much better to cycle small sections. Maybe repeat a two-measure bit 6 times, move on to the next bit, and then after a few minutes review the first bit again. You have to find your sweet spot - a good balance between repeating and covering a decent area. There's an art to this kind of practice.
Now go pump up your piano muscles.