The first day of class was always a tumultuous experience for me as a student, and it's even more so as a University instructor. The combination of excitement, novelty, nervousness and inevitability on that first day is a legitimate rush. Students may seem aloof and disengaged sometimes, but my experience is that students (like most people) get engaged with what they're doing as long as they are trusted, trusting and respected enough to share their interests. I love the process of reaching out to new students to discover common ground between the course content and their goals and experience, building bridges to achieve our shared goals together.
I often share a Zelda Fitzgerald quote at the start of each new course: “She refused to be bored chiefly because she wasn't boring.” I love the jazz age feel of this quote, and I present it as a challenge for students to take control of each class. Everyone gets bored in class (I sometimes find myself getting bored as I teach), so I encourage students to take control of boredom by participating actively in the discussion. If students get involved and frame their understanding through their own experience, it helps them to learn. The benefit of this shared experience helps peers to learn too - and it's much more fun.
Like most things in life, some extra time and effort invested in learning will make the experience much better, and much less tiresome. Passivity is monotonous and dull - and more importantly, it's unproductive. Don't be afraid to stretch your limits. Embrace the novelty, nervousness and inevitability that life delivers, and you will be more alive for the effort.