The human brain can only absorb so much new information at one time, so if you're trying to learn a big block of new material you'll need to break it down into manageable segments.

If you're having a hard time learning a line or phrase, split it in half or divide it into smaller phrases that you can deal with effectively. Try to isolate the hardest parts or the ones you're having the most trouble with and practice them until they're as strong as any other part.

In fact, this is a good concept for your overall playing as well — if you're looking for large leaps forward in your technique, try making the weakest aspect of your playing the strongest one instead, through focus and concentration on that aspect above others until you are proficient.

Be musical in your practicing. Don't think of exercises as just a series of notes you have to make your way through. Instead, treat exercises like they're real music that you have to play with expression and emotional content — that's the way you want your playing to be, so it's what you should always be practicing.