Make a rhythmic exercise out of difficult passages. Before playing the passage, clap or sing the rhythm while tapping your foot until you can easily execute the passage. Do not simply start at the beginning of an etude or solo and wade through. Think about interpretation, tempo, style, dynamics, nuances, and phrasing, even when first attempting to play the exercise. When first reading an etude, look for logical phrase endings during which to breath.
Many students make errors while sightreading because they run out of air in the middle of a phrase.
Practice your etudes and solos patiently by choosing tempos within your reading capability. If you practice at too fast a tempo, you will reinforce bad reading habits and learn pitches and rhythms incorrectly. Return to etudes you were assigned one or two years ago. Before reading them, look for key changes, repeat signs, da cappo markings, tempo and dynamic changes, and consider the interpretative style of the etude. Read them from beginning to end, recovering every time you make an error.