A significant change in my life

I was lucky enough to have met my life mentor back in high school. Before then, I was such a person who played online games all day long and put little effort into my studying. However, everything changed after I met my high school homeroom teacher. He has a similar family background as mine, but he had studied and worked so incredibly hard that he eventually fulfilled his dream of being a teacher. All his life experiences, inspirational talks, and assistance has motivated me to reflect on my own life: if I don’t study and work harder, if I don’t have the determination to improve my family and myself, my parents' efforts will go in vain be in vain! So I decided to study a million times harder instead of playing online games all days. I ended up being the top student in my high school and every result from my hard work has really improved my family.

Any corrections will be greatly appreciated!!!

If you use 'improve your family', this expression is too vague. Although, you use it correctly, the reader wonders how do good results 'improve your family'. i.e. it is too vague. For example, do you earn money each time you get a good result? So the story needs a bit more detail to give a message to the reader.

A significant change in my life

I was lucky enough to have met my a ("my" is correct but since you're talking past is "a" is probably better) life mentor back in high school. Before then, I was such (doesn't sound good) used to be a person who played online games all day long and put little effort to on my studying studies. However, everything changed after I met my ("this" sounds better, as you already introduced this person) this high school homeroom (<- not sure about that) teacher. He has a similar family background as mine, but he had studied and worked so hard that he eventually fulfilled his dream of being becoming a teacher. All his life experiences, inspirational talks, and assistance has motivated me to reflect on my own life: if I don’t study and work harder, if I don’t have the determination to improve my family (I need to know what you meant here to provide feedback) and myself, my patents' parents' efforts will go (will does assures that it will happen would is hypothetical) would be in vain! So I decided to study a million times harder instead of playing online games all days. I ended up being the top student in my high school and every the results from of my hard work has really improved helped? my family.

Any corrections will be greatly appreciated!!!