Avoid Cliches. There are a few standard reasons why people become doctors, and so it is very easy to fall into cliched expressions and ideas. Though it's fine to express a commonly_held notion, try to find a personal way to express it. For example, rather than write "I want to be a doctor because I want to help people," discuss the ways that you have shown your generosity and kindheartedness in the past; bring specific examples__such as your volunteer experiences__so as to avoid a direct (and possibly cliched) declaration of your point. Sometimes cliches are unavoidable; just make sure your essay isn't full of them.
In order for there to be tension in your personal statement, it will help to describe a highly charged incident, part of a particularly difficult period in your life. Whatever it was, you will maintain your reader's interest for that much longer. The example below shows perfect tension and suspense build up _ "When the airmail letter arrived bearing an American stamp, I knew immediately, it was from my university with my degree results, and I tore it open as excitedly as if it were a birthday present. With trembling fingers, I took out the sheets of thin blue paper _ and my heart started to pound as I began to read."