The most common advice you will hear is to do more sports. Well, yes but what do you do if you are not that into sports and don't want to start something? It was me in early 2012. I was young, and I was on my semester abroad, and I had to do something.
Just take a minute for yourself here and think about the most influential people in your life. People like your parents, friends, teachers come to mind, they all affect your life and probably taught you a thing or two. You naturally aspire to be like them, you count on their advice and you would follow them to the end of the world (a bit romantic, I know).