Chopin Polonaise op. 40 no. 2; Difficulties with bars 19 - 39

[nikolaslund]

I post this, because I for some time have struggled with playing the faster section that constitutes bars 19 to 39 of Chopin's Polonaise op. 40 no. 2. Initially I am able to keep up the tempo, but after reaching the "climax" and continuing beyond it, I find my right hand - more specifically, the 3rd, 4th and 5th finger - incredibly tense. I would also say that I generally have problems playing the section fluently, if that makes sense as a description. So, my question is how I can "repair" these faults, or avoid them. I realise it might be difficult to give concrete advice, given the fact that I have only given a general description of my problem, but anything would be appreciated.

 I would like to add that, when playing other pieces such as the Prelude of Bach's English Suite no. 2, Schubert's Drei Klavierstücke, or Rachmaninoff's Prelude in C charp minor, I run into the same issue, which leads to me not being able to complete the pieces - something quite disheartening.