I'm technically in the start of my career (26 years old) but if I could go back to my first year in the university what I would do is investing heavily only in the things I know I like. For me this is backend development (Java+Scala) and a certain OS (Arch Linux). If I've done this I would be an expert right now. What I did instead was trying a different thing (languages, OSs, technology fields etc) every single month until I was sure on what I want. It's the natural process though so I'm not disappointed.