Define 'smart'
If by smart, you mean: memorisation, textbook learning, studious and acing all your exams
Then you should kill your social life, sever all ties to any social sites (including this one), study all day and all night at home. Eat well, exercise well and sleep well. A healthy body = A healthy mind (although this type of mind is probably unhealthy anyway)
If you mean: good balance of knowledge and common sense
Then you should be splitting your time 'evenly', 8 hours work, 8 hours play, 8 hours rest (yeah maybe in theoretical land). Eat well, get all your nutrients and vitamins, read high level books, take daily logic puzzles/brain training challenges and immerse yourself in social situations
If you mean: having fun and making the most of life > studying
Then you should kill your study life, sever all ties to any study sites (including this one), party all day and all night outside. Eat big, exercise heaps and sleep sporadically. A drugged up body = A hyped up mind
My answer to your question: Be yourself. Be the best that you can be. Don't have any regrets.