As someone who's way too ambitious myself, I think the depression comes from having expectations that are as big as your oversized ambition. Which will obviously backfire.
I could do something like what you're planning, if I really wanted to. I have the tools, and most of the knowhow, and I've thought of making something like an animated opening many times before.
But I ALSO have the wisdom to know that I wouldn't even get a day into the work before wanting to throw myself off a bridge. I've quit so many animation projects after drawing just ONE frame, it's not even funny.
But over time, I've learned that it's okay to quit. It's okay to feel overwhelmed and under-equipped to take on the demands of your imagination. You aren't actually an 'art machine'; you're just one mortal human being. So give yourself a break. Dream as big as you want, but lower those expectations of what will actually happen to the level of reality.
Of course, that doesn't mean that every time your ambition flares up, you should just ignore it, or try to stamp it out completely. Every once in a while, it's good to test your limits; see how far you can get with one of your big ideas, even if it's only halfway.
If you can't do music, try just doing the animation. Or if the fact that you can't do the music is really bugging you, try looking for ways you can learn to create music. Or maybe jump all the way to the end of the process and see how you would go about turning all that stuff into an actual video (this is actually a very important step...there's nothing more frustrating than pouring your heart and soul into a new project and then realizing at the last minute that you don't even know how to share it with anyone).
That's the great thing about having ambition: it pushes you to keep learning new skills and keep gaining new resources, even when they don't turn into tangible results right away.
Despite my hatred for animation, I have 4 animatic episodes under my belt. Sure, none of them are more than 3 minutes long, and it's taken me two years just to get to that many, and it's not even 'real' animation...but it's something. Something that I can enjoy watching, and something that taught me so many things about editing and sound design and storyboarding that, two years ago, I probably would've passed off as 'too ambitious'. Who knows what I'll be doing two years from now? Probably still not as much as I'd like...but I'll be closer to that ideal.