You always see the "things I would have said to my freshman self" but why don't you see "things my freshman self wants to say to the sophomore me?" 

I believe that learning from your mistakes is an important part of life. Looking back over your life and saying to yourself that "it is okay that I kissed that guy - I learned something from it."  is part of growing up. Although there is one flaw with this: people like to wait a few years (or even more) before deciding to learn. Either that, or they don't take along the knowledge with them.

Now that sophomore year of college has in fact started for me, I think it is an appropriate time to remind myself of a few things. 

• Grades are in fact the most important thing about being at school. You came here to get a degree, so be sure to work hard for it.
• I know Netflix is calling your name but so is homework. 
• Start homework/papers/projects right away. Don't say "after this episode on Netflix I will" because we both know that you'll keep saying that till it's 3 a.m. and you're too exhausted to focus. 
• Keep your planner(s) up to date. In the middle of the semester is not a good time to stop writing in them. (Lesson learned.) 
• Flashcards are in fact your friends.
• Greek life can be overwhelming - if you need to not go to something, just say so. 
• There will be other date parties. 
• Also - not going out every night is perfectly okay. Not going out at all is also perfectly okay.
• Say hello to all the new babies; remember how scared you were when you went to the house for lunch? 
• Your sisters are here for you - if you need to rant about professors, family members, or need help with homework, tell them. 
• Sisters are the best friends possible.
• You are going to have to work at making friends - they don't just magically appear. 
• Getting lost is not that big of a deal. Just ask for help. No one is going to judge you. (Also, checking the campus map as to where your building is is again fine. No one can see your laptop!)
• You can wear running shorts and a tshirt everyday to class. No biggie. 
• If you feel yourself getting sick, don't say "Oh I'll be fine." Go to the clinic - that's what it's here for. 
• STOP SPENDING SO MUCH MONEY. Get a budget and stick with it. It can be hard - especially if you have a rich, British roommate who always needs something at Target (aka Starbucks) - just remember to say no. Or go with but leave your wallet at home so you're not tempted to buy something. 
• Call your mom and dad every once in a while. And grandparents too.