When it comes to studying there can sometimes be a gap between what you intend to do and what you do do.
The effect of this is that you get less done than you want.
Sometimes this can simply be down to some unexpected event getting in the way.
However, if there is a pattern to this happening then you need to look at why. And one common reason why this can happen is if you are lacking motivation.
If you’re having difficulty getting yourself motivated, try and get to the root cause. Otherwise I’m afraid you may be destined to keep repeating the same pattern!