It's great to be on winter break. I hope everyone's semester was decent enough. If not, well I know people can relate. Personally, this semester could've been better on soooo many levels but I have a sure-fire plan to make next semester a redemption.
First, you gotta relive the semester out in your head to see everything that went wrong. Yes, this sounds terrible. Honestly, it will be. But the purpose is to see what you could've done better. Maybe you could've asked for help, gone out less, actually got some decent sleep, or all of the above. Whatever the case may be, you just need to document solutions to your screw ups.
Next, you need to plan out how you're going to better next semester. You can make these apart of your New Years Resolution, kill two birds with one stone. And when I say plan, actually plan! Get out your handy dandy Google calendar and mark it up with your class schedule. Carve out time to fix whatever you need to work on. For me, it was a lot of things but the main thing was sleep. So I need to put in specific times where I can get enough sleep during my busy schedule.
Finally, like Nike, just do it! Easier said than done, I know. It's going to be hard but you have to follow through on your goals if you really want to improve. Before you even start to lose motivation, tell some people about your goals so you can be held accountable later. Also, write them down or type them out in a nice pretty font and hang it up somewhere that you always look. Over your desk is a good option.
Best of luck with the new semester!