It seems to me that most students who get into trouble writing essays find themselves in trouble with the opening paragraph. Usually they are trying to state a thesis and say what they are going to say in their paper. There is no law that says you have to write the opening paragraph first. You might write that paragraph last of all. Nobody knows in advance what he is going to say before he says it. If you know what life lesson you are going to tell the reader about, then I believe you should start by writing something about the life lesson itself. What did you learn? What was the event that taught you that lesson? Why do you consider it valuable? How has it changed your life? Naturally the introductory material has to come first, but it doesn't have to be written first. The same applies to the title. The title comes first, but it doesn't have to be written first. Many authors have written entire books and haven't given them titles until the books were totally finished. Words are easily rearranged, especially in these days of computers with word processing programs. You are not carving in stone but working, as it were, with modeling clay. You can start anywhere and say virtually anything you feel like saying. This, of course, means that you will have to write more than one draft--but every paper a conscientious student turns in should be the final result of several drafts. James Thurber was one of our best American writers. He made an often-quoted statement about writing.
Don't get it right, get it written.
Thurber said that his own first drafts were usually horrible. But he would revise and add and delete until he was satisfied with the final result. You can't revise something that doesn't exist. You have to have something on paper. That something should probably be based on explaining who, what, where, when, why. Don't try to be a prose stylist. Just say the words. They may end up sounding a lot better than you think. Be honest. Teachers appreciate honesty and sincerity and real thought.