It seems quite ironic that we always need to spend a good amount of time playing slowly and carefully in order to build up to breathtaking speeds in technical passages. Remember that you need to establish muscle memory and starting slowly is the sure pathway to success. But, play mindfully so that you are fully engaged. ALWAYS play smaller sections and try playing them in different octaves (for example if it's a low register passage, try playing in the middle register since the fingerings are mostly the same), Try playing the passage from right to left: all these tools can help 'wake up' the brain and fingers and lead you to success. When going for the final push of fast tempos, I try the 'add a note' method: play two notes in the passage at tempo, repeat several times, then three notes, repeat, until you have a full beat's worth of notes. Then add on the next beat's worth in similar fashion. And if you make an error, really analyze WHY it happened: until you figure out what went wrong, you might be frustrated and keep repeating the error. Building reliable and sparkling technique is the result of careful and deliberate work!