Hello,I'm currently a 1st year undergrad at a conservatory studying piano performance.The thing is that whenever i finish my daily practice, i don't feel like i accomplished anything, i feel as though i leave with what i arrived with, so to say. So i am wondering if i am practising efficiently, or if i am just wasting time. I recently met Stephen Hough and he said that he would rather practice 2 hours of fully concentrated rather than 8 hours, or something along those lines. How do we practice with full concentration? If i recall correctly, Barenboim said something along the same lines. Thanks.