Yes, you have to be precisely honest and quite revealing and candid to write a successful autobiography. And obviously, you need to describe some hardships of your life to show how you coped with that or how it influenced you. However, we strongly advise you to describe the thing that you feel rather calm about when writing. For example, you are writing about other students picking and making fun of you at high school. If you still feel like wanting to kill them all, it would be better to avoid this topic or mention it slightly. Why so? Because your feelings will leak into the writing and make your reader feel subconsciously uncomfortable.

Organize what you've written according to cause and effect and action and reaction. Ordering events according to cause and effect is a natural process. Your car broke down, so you called a tow truck. That's cause and effect. You received a promotion, so you bought a house. Action/reaction happens paragraph by paragraph. He said "No," so you said "Why?" That's action/reaction. She set a wet glass on the table, so you placed a coaster under it, and remembered how your mother used to crochet pretty little coasters and starch them. That's action/reaction.
Develop a central theme, main idea or thesis that clearly explains the purpose behind your autobiography. For example, your theme might be about how you overcame obstacles to become a stronger person, or it might explain why a particular passion -- such as mountain climbing or rescuing animals -- is so important to you. Back your theme with details and background information about your life experiences. For example, you might explain that your dad is in the military, so you've had to learn how to adapt quickly to new schools and unfamiliar environments. Or, you might discuss what it was like growing up in a poor, single-parent home, but how your family was always willing to take in injured or stray pets.