I would like to learn responsibility. What's the best way?

I am living in a world where everything has been handed to me for free. I currently live with my parents who have provided me with a home to live in, a well paying job, pay for my college education which I am currently undergoing, home gym…etc. but I rarely utilize these blessings to my benefit. I constantly waste time doing unproductive things when I can be using these things, which many people do not have the luxury of having, to reach my goals. I am stuck in a cycle of laziness and disappointment. As a result, I am overweight and my grade point average has dropped considerably, which will make it difficult for me to enter professional school after college.
I feel that if I can learn to not take these blessings for granted and learn to become responsible for my life and the results of my inaction, I can escape the vicious cycle.
What is the best way of doing this? I am contemplating moving out on my own and becoming completely self sufficient. Are there better ways?
I am 18 years old and I’m halfway through my second year of college. I’m planning on going to medical school and my GPA is steadily sinking, so I need to do something about it soon.

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