The above answer by sdesabato is excellent. I agree with it entirely--especially about writing everything out in many paragraphs and then selecting the best for your final draft.
I have one other suggestion which might make your job easier. You might begin with writing about how you felt when you were back in school after all those years. If it felt good to be back, that should have proved you made the right decision. Then you might explain how and why you made the decision.
I suspect that you found school was a lot more interesting and enjoyable after being away from it for so long.