| To quote Simon and Garfunkle - Slow down, you move too fast...
Sometimes to move forward we have to slow to a crawl first. Slow yourself right down, and work on playing the same material at a stupidly slow tempo with relaxed left and right hand.
Each note, take the time to relax yourself - ask youself "Is this the least possible amount of pressure I can apply to make the note sound properly? Is this the smallest amount of motion I can do to move my fingers up and off the string". You will be shocked at how relaxed you start off and how tense you become in a very short number of notes.
I did this very recently when I had hit a wall and found that I lift my fingers way too far from the board during my descending scale runs, but I'm fine on ascending runs - I tend to try to get my fingers out of the way as I play notes a fret lower. Slowing down and practicing at slow speed helped me see this and also helped me correct it. My top speed jumped by 20bpm once I sped up again.
I also found that I tensed up the longer I played, especially in fast pieces - I regained speed and tone each time I lowered my shoulders and relaxed my grip, but I went up and down through the song. Playing it slowly helped me remove the tension. | 
