Two things I would say.....Practice playing at a speed that you don't make any mistakes with and persevere when there is something you can't do, it will come good with slow practice.
These two are intertwined and echo what Michelle said. Ok three, Learn the fretboard and four pick the odd song that is outwith your comfort zone, when you master it you will be a better player for the experience.
Five...Learn new techniques and put them in the toolbox for use on other songs, like scratches or mutes etc. Ok there are loads more, but that's probably enough for now.
Cheers,
Tom N.