Obvious doesn't count.
This is YMAS.
The ability to be realistic with yourself. If you just make excuses and can't be honest about what needs work, you're screwed.
OP: Assuming you are still reading this. Two important things, do both at the same time.
1. Get and stay in the best shape you can.
2. Learn the basics of your chosen art, and never, ever stop working on them.
Good luck in your training.
The most important attribute to you is the one you posses and can use. If you are fit make them gas if you are fast beat them with speed and intensity etc... The most important thing is using what you got. As you “master” the basic you will start to develop your “style” of techniques and strategies that work for you all this course means nothing unless you are “staying alive” as the others put it which means training with aliveness. If you do not “stay alive” you will not find works for you so you must find a school that does as much alive sparring as possible. Also listen to your instructors and seniors they know more then you.
This is the most important thing in martial arts.
YouTube- CaramellDansen (Full Version + Lyrics)
Knowledge. Honesty. Trust. At the centre of that triangle is the most important thing in martial arts.
Other than that, what Kempofist said.
Most important thing for me is balance between safety and sparring closest to reality.
What? You stop practicing when you break something in your body.
Every serious answer before mine are great.
Doesn't matter how dtrong, fast or tough you are. Doesn't matter how many technicues you know or how alive you train(well yeah it kinda does, but STFU I'm trying to make a point here).
The most important thing you'll need to be a succesfull martial artist is guts. Courage. A set of brass balls et cetera.
Like a great meme once stated:
Nobody ever achieved anything by being a *****.