It's normal. However -- and I say this with respect, as it's true for all of us -- you have to realize how dumb you were in your teens. Back then, your brain was about at sharp as it will ever be, but you didn't know very much. Almost everything you encountered was truly new to you in some way. And novelty is fun, especially if you're capable of making sense of it.

If your 13-year-old self met you today, he or she would be astonished how wise and experienced you are. And you'd probably be amused how eager but naive your younger self is.

In some respects, this transition is unavoidable. You're supposed to get a little bit jaded as you get older. You can't be excited forever that today's the day you first saw a giraffe up close or discovered type inference. Eventually people will expect wisdom, experience, and judgment from you, rather than raw enthusiasm and energy. But does this mean your future needs to suck? Not at all.

The key is using your experience to see a situation differently than you would without that experience. Think back to your first week on your current team and how little you knew. What would you tell yourself if you could teleport back to then? Are you taking that advice now? If not, why not?

If you keep applying accumulated experience to your current decisions, then either you'll continue growing, seeing repetitive things differently over time, or you'll decide that your current environment is toxically static and can't stand up to the kind of introspection that you demand, and you'll move on. Either you change your perspective, or you change what you're looking at. Either way, you never see the same thing twice.