I've always liked the idea of creating a magnum opus. I've always thought of everything I've written so far as leading up to something that takes all of those ideas and uses them to the best possible end-- where everything comes together in a way that's clear and poetic and excellent overall. I suppose all great writers (or musicians, filmmakers, artists, etc.) have that one novel or that one film or album that achieves everything they've set out to do and stands out as their absolute best... I suppose it's more of a term reserved for critics, but I think it's also a good way for anyone serious about what they do to challenge themselves. Also, I think it's important to create a foundation from which your literary (or whatever) voice can spring... like your own world that comes alive (even more alive than your immediate reality) because of the time and energy invested in it. I think if you can create a solid foundation like that, you'll always be able to add to it, and ideas will always come out of it-- you can keep coming back to the characters from new angles and discover new things about them, and add in new ones that bring more to the table. Does anyone else have this desire?
I'm happy with being an under-achiever. You know something about the value-givers, the authorities, the teachers? They're dead or in nursing homes. And they haven't been replaced by anyone worthy of respect. I sit beside the fire and think of people long ago, And people who will see a world that I will never know. But all the while I sit and think of times there were before. I listen for returning feet, and voices at the door. -- John Tolkien
I love the idea of a Magnum Opus, and being into writing and music keeps that distant goal even more interesting. I would love to write a dark and depressing novella, a terrifying film script or short story, and a truly bleak/oppressive piece of music. I think that the Magnum Opus concept should not be one impossible goal always looming just out of reach, but should several more reasonable goals. Keep your writing interests diverse, and reserve a "best" for short story, novel, etc.