Well, I have my signed photo of John Petrucci to motivate me!!!
The way that I schedule my practices is as follows.
I write a BIG list of things I want to work on this month.
Each day, I pick things from the list, and work on them for a max 10 minutes each. This way you can give full attention to the technique without getting bored and lazy/sloppy.
Don't forget to check things off the big list as you do them each day!
I spend about a solid two hours a day doing this, and if you stay focused you really accomplish a lot. I used to just pick a lick and practice it for 2 hours while I watched a movie. That is a no-no.
If you stick to the 10 minute max, even if the time is over and you aren't satisfied with you progress, stop. That way, the next day (or maybe two) when you get back to that riff, you are 100% motivated and focused.