Promise yourself you'll only do 15 minutes.
Do pomodoros (similar to above).
No zero days/don't break the cycle (made famous by Seinfeld).
Leave a small task to do for next time, making it easy to get into it.
Set a realistic goal/project to make with your learning rather than learning open ended (could be the reason for your plateau, as it can be interesting to get into something initially but hard to maintain after the low hanging fruit is learned).
Blog about each topic/micro topic/learning.
Get peer feedback/reinforcement by announcing to someone or a community what you are working on or learning and when you will finish.
Good luck!