Most of us have been confronted with music that's too difficult for us to play.

This 7-step process can help you learn such a passage sooner:
        

1. Through experimentation, decide on the best fingering, picking pattern and fingerboard position.
2. Rewrite the line without any rhythms so you can focus in on the notes.
3. Play with dotted rhythms, long, short, long, short, etc.
4. Reverse the dotted rhythms, short, long, etc.
5. Play the line in triplets.
6. Start the triplets on the second note.
7. Start the triplets on the third note.
     
By moving accents around, you gradually remove the obstacles that exist between each pair of notes. With dotted rhythms you can play each pair of notes faster than you could play the whole line.  If after going through this process you still have trouble with the original, repeat this process on the line every day until you get it.   Use a metronome.