Help with Beethoven's Pathetique Sonata Movement 1...?

I seem to have trouble with the section of the first movement following the part where the right hand crosses over the left . After practicing it slowly and increasing the speed each time , I can play it up to to tempo correctly without trouble . But when I am playing it say the next day without starting off slow, my hands are more tense when playing it And they get tired after playing twice through. I've been practicing it for a while now but just can't seem to play That part at full tempo right off the bat without my hands getting somewhat tired even after warming up(scales, etc.) I have no problems playing the rest of the piece at tempo but with this part and can just barely get through it without starting off slow And working my way up because my hands seem to get tired which affects the performance of the section directly following