The way our society is structured we have to earn everything we desire: the respect of others, the right to be heard, the trust of those around us, our standing in society and especially the physical things that we desire. The problem with this mentality is when it leaks over into our spiritual understanding. We start to believe that we have to do enough "good stuff" to earn God's favor and to keep our standing as Christians. If you have spent anytime in a real relationship with God you know that is not possible, but it certainly doesn't stop us from trying. The side effect of that is a poor self-esteem and an increasingly negative view of yourself since you can never "measure up" to the standard.
It also makes it difficult to keep the two greatest commandments-love God and love your neighbor as yourself. I can love God (or at least profess it), but it's difficult to love others as yourself when you don't tend to love yourself too much based on your own multiple failings and screwed up decisions. At the root of it, it comes down to whether you believe that God loves you for who you are or not.
"Do you really accept the message that God is head over heels in love with you? I believe this question is at the core of our ability to mature and grow spiritually. If in our hearts we really don't believe that God loves us as we are, if we are still tainted by the lie that we can do something to make God love us more, we are rejecting the message of the cross." -Brennan Manning