In the sense of a letter, it should have an opening, a body and a closing. I tend to use the opening to identify myself, the body to tell of my strengths and the closing to tell people of my purpose.
Opening - my name is Stephen. I live in Amsterdam and work as an online tutor. I have a Master's degree....
Body - During my career, I have experienced this and that and have grown and learned from this and that.
Closing - I thank you for the time you have spent with me. I hope to see this and that occur and hope for a future with this and that
Be proud of yourself but remain modest. People will want to hear of your strengths but don't want to hear that you are a superhero. ;-)
I hope this helps and my best with your essay.