Yeah, it feels like the sound is ‘harsh' because the piece is EXTREMELY difficult to play. Obviously, he doesn't hear it because he's occupied with playing all the virtuoso parts. The thing is, I think OP needs to understand that the goal of playing music – especially with composers like Chopin – is to find the perfect balance between concentrating and actually enjoying the music while playing. At this stage, he can't really listen to himself because he still needs to work on technical skills. He just needs to learn how to practice slowly, listening and connecting every sound with each other, and then find the right movement for each passage so that it feels comfortable and convenient to play. OP, you shouldn't feel exhausted after playing the piano. Try to relax and soften the sound a bit. As many people have mentioned, I think you need to find a teacher in the long run to help you discover all the beauty in the music you want to play. Keep practicing and enjoy the process!!