What I do is take my practice in incriments of an hour and a half. This is the time that a human mind is said to be able to focus for.
I will use an hour and a half on Rach, an hour and a half on Mozart, an hour and a half on Chopin, an hour and a half on Liszt technical excersizes.......
and later on I will add Bach into this.
With these incriments, even with just 15 minutes break, it is so much easier to practice.
I have a timer that I baught from walgreens, and whenever I screw around, I will pause it.
Many people say quality, not quantity, and I agree, but when you can combine the two, that's when you get really good, and that's what I'm attempting to do.
Of course, I'm still lazy and averaging 3.