From PBS.org: article on myths and facts about attachment

Secure attachment has to do with your child knowing that you are trustworthy, knowing that you are there, that you will respond to his/her needs. Secure attachment is vital. Attachment in early childhood, secure or insecure, has been found to have an impact in future relationships. In other words, if, as a young child, you were securely attached to your caregiver, later on, adult relationships will be easier for you.

Attachment is something I am very passionate about. Some day I would love to have the time to write a long post on attachment. In the meantime, here is this article:
http://www.pbs.org/thisemotionallife/childhood-attachment