Very ala Petrucci/Gilbert, let's get our pick hand fired up by blowing through each and every mode of G major.
With each full ascend (occupying 5 bars) we see the same "up-down-up" pattern. After each of these ascends, however, we're faced with a quick descend in groupings of three. Note that these groupings are not triplets, rather, played at the exact same speed and velocity as the rest. Due to the change of pulse, make sure you analyze the tail end of each 3-grouping descend (ie. last three notes in bar 7) as the turn-around has a tedency to cause some fumbling from time to time.
After making your way through the entire exercise, notice the repeat sign - yes, that's right, do it again! Do it as many times as you can to feel that burn - whether it's after the first 4 bars or the first 4 full repetitions. It's important to examine your picking hand and make sure that there are no "distrurbances" which could possibly be affecting your over-all endurance, ie. tense muscles, hand/finger ergonomics, etc.