Because Barack Obama is of mixed race origin, the absence of his Kenyan father throughout most of his life caused him to have something of an identity crisis. That is, he knew he had a Kenyan family and heritage, but had no connection to that side of his culture while he was growing up. He substituted the male role model with his Grandfather, who he speaks of in glowing and affectionate terms throughout this book.
He still wandered a bit when he was a teenager, experimented with drug use, and got involved in other negative activities. He attempts to adopt some Indonesian culture as well during his time livign there with his mother and stepfather. All of these were coping mechanisms and strategies that didn't really help all that much until he spent some time with his father, and traveled to Kenya to meet his extended family.