How to deal with parents expectations?

[18M] The thing is I have been in this loop of instant gratification for 3 years and now I just started my journey to heal myself from the scars that I did in these 3 years.

But the thing that doesn't let me sleep is the fact that I have let down my parents. They are the only reason I am alive today. But they are extremely disappointed with myself to a point that they don't take me seriously, whenever I fail at something, they shout at me and scream which I understand because they are also human and it's painful and to say they are betrayed by me.

It's extremely traumatized to the point that whenever they shout at me, I feel pain in my chest. And I know for a fact that it will take a very long time to show them results. Maybe 6 months to a year.

In this time how can I defend from this?