I messed up my 11th, what to do for the 12th while preparing for JEE?

For several of us when we move from 10th to 11th we often find ourselves in rather uncomfortable bewilderment when it comes to our educational experience. The scenario is more or less the same irrespective of the boards to which our schools or our educational institutions are affiliated. Hailing from the ICSE board myself, initially, the upgrade to ISC, the science stream was unnerving. As the content of each course slowly and steadily unfolded, the upgrade from ICSE to ISC was far too much food on the platter. Several of my classmates also reported the same uncomforting scenario. Not only ISC, the sudden and vast change in content in the CBSE board was also brought forward by several peers.