So I just went through a period of time equating to around a month and a half where I didn't practice very much at all, and now that I'm getting back into practicing I can't seem to get the focus I had before I stopped practicing back. I'll spend about 5 minutes on a lick or riff in front of a metronome, get bored and find a completely different riff. Any advice guys (and yes I do have joels book).
It is really hard to focus on a specific exercise for me too. What I do sometimes is playing different exercises to the same tempo, and switch between them so I dont get bored by playing the same stuff all over again.
It is all about self awareness, so when you understand that you are playing not what you want to play, you force yourself to switch back. If you really want to practice one exercise, think about you playing it at a goal tempo, understand how good it will feel, and after that, take a big piece of paper and write at it something like "PRACTICE THE DAMN EXERCISE" and hang it on the wall in front of you. Every time you feel you start to play something else look up, read the message and switch back. Try that and tell me if it worked for you