Never be satisfied.
"The drive to close the gap between near-perfect and perfect is the difference between great and unstoppable." -- Tim Grover
Even after you achieve a goal, you're not content. For you, it's not even about the goal. It's about the climb to see how far you can push yourself.
Does this make you ungrateful? Absolutely not. You're entirely humbled and grateful for everything in your life. Which is why you will never get complacent or lazy.
To quote Jim Rohn: "The way to enjoy life best is to wrap up one goal and start right on the next one. Don't linger too long at the table of success; the only way to enjoy another meal is to get hungry."