Each of the four years of Engineering has a different purpose, and a different set of challenges. PSecond year gives you the skills you need to become an Engineer. Take the time to understand the theories. In third year, you will become an Engineer. Focus on what interests you.
Fourth year is a time for exploration.
Find a challenging design project. And relax, third year is behind you. Whatever year you're in, get involved. Make time for your friends. Four years are over before you realize it.