Growth – Is the belief that you can get better at something. See the book “Mindset: The New Psychology of Success”
Grind – Is doing your best with all the things that needs to be done. Grind is everything that has to do with what you love, it’s not just directly related to your passion, it’s the other stuff as well. See the book “Relentless”
Grit – Is the ability to stick to something. Adjusting and overcoming in order to continue chasing your goals. See the book “Grit”
Basically, believe that you can do more and better. Set the goal of being the best version of yourself. Come up with a plan. Give your best effort to what you are doing. Stick to it and overcome the obstacles that pop up along the way.
Here is the simplest explanation:
GROWTH – Believe you can.
GRIND – Do the work.
GRIT – Stick with it.