Practice the part of the song you always mess up, not the part you like playing for people.

Practice drifts toward what feels good. You play the part that sounds impressive, get the small reward of doing it well, and the rough section stays rough because it is unpleasant and nobody is watching it. Time spent is not the same as time spent where the weakness is.

Start the session with the hardest eight bars, slowly, before you have warmed up your confidence. Loop it until it is boring rather than until it is right once. Give the enjoyable part the end of the session, as the reward it already is, and let the difficult part have your freshest attention.