I am of the latter view although it is hard to resist the trap of fixed mindsets. A great source of information on this is the following video;
At the present stage of my journey through life all the things I once thought were fixed have come to unravel, all the foundations have crumbled, all the rugs have been pulled and safety nets burned.
I no longer know exactly who I am or what I am doing and it is a very frightening thing to face; it would absolutely devastate someone who does not believe in a Growth or Fluid mindset in which anyone is capable of accomplishing whatever they desire simply by believing they can and following through.
What does this have to do with Martial Arts? First off, if we allow the process to take place, training can highlight points of our fixed mindsets and provide some insight into them.
We can see them for what they are and use them, turn them to the development of the mind and free ourselves from them.
There is no limit to the things a person can accomplish if they simply have the courage to step outside of that box, to allow those foundations to crumble, to entertain the thought that they know nothing, least of all themselves... There is always something to discover, always.
Who am I? What am I capable of doing? What am I actually interested in? How can I use my previous experience to push myself farther?
Lots of people talk a lot about fighting when it comes to Martial Arts, but they seldom have anything to say about the mind or spirit, those that do either dismiss it or what they have to say is complete Bullshit and puts people off of the subject entirely.
You have to delve deep into yourself in order to improve upon yourself, even if you are a practically minded Martial Artist, you have to delve deep into those recesses that most do not have the courage to explore... It can be very dangerous, yes, but also very fulfilling... You WILL lose yourself more than once, but in the end you find out who you really are and what you are capable of.