How to Play Fast and Clean
Wanting to play faster almost always makes you tense up more - hit harder with the pick, press the strings harder, concentrate more intensely. But real speed comes from the opposite: minimal tension and the most economical motion possible.
Speed is the absence of extra motion
The difference between a fast and a slow guitarist is almost never that the fast one physically moves their hands quicker - it's that a fast guitarist's motion has nothing extra in it: the fretting fingers don't lift higher than needed, the pick doesn't arc widely, the wrist doesn't tense beyond what's necessary. Removing extra motion almost always gains more speed than trying to move faster with the same motion.
Tension is the main brake on speed
A tense muscle is physically slower than a relaxed one - that's not a metaphor, it's biomechanics. That's exactly why 'trying hard' to play faster almost always backfires: the tension that comes with effort slows down the very motion you're trying to speed up.
Checking for extra tension
While playing, periodically check: are your shoulders raised, is your breath being held, is your jaw clenched - these are indirect signs of overall body tension that carries into the hands too, even when the hand technique itself is otherwise correct. Deliberately relaxing exactly these spots often gains more speed than working on the technique itself.
Slow practice isn't the opposite of speed
Slow, deliberate practice at a low tempo is exactly what builds the economical, relaxed motion that produces results at high speed - it's not a 'warm-up stage before real fast playing', it's the actual mechanism speed is built from. A guitarist who only practices at a high tempo usually reinforces tense motion, not fast motion.
Cleanliness beats speed at every stage
A fast but sloppy passage sounds worse than a slow, clean version of the same passage - listeners forgive a slower tempo far more readily than smeared notes. It's worth raising the tempo only once a passage is clean at the current one, not because you want to play it 'like the original' regardless of cleanliness.
Try it in practice
Open the metronome