Here I'll talk a little more about those two important motivators I mentioned previously. Again, they are 1) the music itself and 2) our own personal improvement. In practice, these two things translate into playing songs and practicing exercises (the fastest means for technical improvement). In this section, I'll be talking about striking the right balance between them.
What you practice determines your niche, or identity, as a guitarist. There is no right or wrong here, but different approaches produce different results. For example, if you learn a lot of songs, but never delve into any real skill-intensive exercise-type practice, you'll likely never develop a lot of technical skill as a guitarist. Now there's nothing wrong with this, if this is what you want. Maybe for you, songwriting and melody is where it's at, and I for one would never argue with you there.
On the other hand, some of us are turned on by speed and precision. We want to take our skills to the limit. For this, breaking things down and isolating them into repetitive exercises is the ticket. This builds speed and technique the fastest way possible. That's fine, too.
But there is the potential danger here. Many times I've seen players who really get into skill-building exercises, and at first it fuels an intense motivation. They see so much improvement, so fast. But inevitably it levels out at some point. They reach a plateau and they can't seem to break through. But they keep pushing anyway, and one day, they suddenly realize that they don't really feel like practicing any more! (I, too, burned out on technique once upon a time, so I know about this whole trip from personal experience. )
Exercises alone, without music, are sterile. The bare skills by themselves, without an application, are useless and unfinished. They are potential without form. Music is always the destination. Music is the point of it all. If this is firmly etched in your brain, you'll be too busy being inspired by great music to get burned out or discouraged! Obviously, for those of us in this boat, we have lost sight of the first motivation--music--because we got a little too carried away with our own technical improvement. We are out of balance. (A decidedly un-90's thing to be, don't you think? )
Why do we continue on down this path if we see that it is burning us out? Well, we are all creatures of habit. Until we make a concrete decision otherwise, we tend to repeat what we have done before: even when it is uncomfortable or it is producing effects we don't like. So we must look at our situation and make a new decision.
Re-assess. Take a little time off. Go see a concert. Buy a few new CDs and listen to something else for a change. Search for some new inspiration. Maybe you won't even play guitar for a few weeks, but so what? The important thing is to rediscover your inspiration. And when you do, it'll take you far beyond anything you could accomplish by sheer discipline or force of will alone.
Playing music alone, without any concentrated exercises, will likely limit your level of technical proficiency. On the other hand, practicing a lot of skill-intensive exercises will produce fast technical improvement for a while, but eventually it will level off. And if you keep going at it hard, it'll likely burn you out. The answer lies in finding the right balance: the right amount of inspiration from the music itself, and the right amount of inspiration from our own improvement derived from skill-intensive practice. Of course, the right balance is a little different for each of us, and it may change over time.