I'm afraid the text is very hard to read. Also, it is rather long.
Here's a start:
When we are born, it marks the beginning of a new life. We all grow and change through our lives. I believe that Erikson’s Psychosocial Theory of Development best describes a change in one’s life. Erikson’s eight stages of psychosocial development starts when you are born till your death.
1- Don't mix you and one as pronouns. Use either, but do it consistantly. Eight stages would make the verb 'start' plural and start does not go with the phrase coming after it.