Too many times when I see someone practicing some type of guitar shred, they are in too much of a rush to succeed. They are playing faster than they are really capable and it sounds pretty sloppy. The cure for this is to take it slow.
I am sure you have already heard a zillion guitar players say to practice difficult stuff slow. I know I have. But it is something worth repeating again and again because it is so true. You have to practice tough stuff slow and practice that way a lot. Don’t just practice a lick slow a couple of times and then go right back up to full speed. Be honest with yourself, if you are playing at a fast tempo but it sounds bad, slow it down and make it sound good.
One good way of doing this is to practice with a metronome at a speed you can play the lick perfect. Again, be honest with yourself. If it isn’t perfect, slow it down some more. Once you get it write down the date and the metronome setting. Do this everyday. You will be inspired as you can see how far you have come after a few weeks or months. A good rule of thumb is to only go up a couple of metronome settings a week.
One last thing that is really important. Don’t always practice with your gain on 10. Spend time each day practicing your licks and stuff with a clean guitar sound as well a guitar sound. You may hear little things this way that you may have been covering up with distortion.