It might be hard to believe that we fear love and happiness, but it is a real dynamic that happens in the mind. It is easier to understand if we consider the mind to be a living being with many different aspects. If we attempt to change our beliefs and behavior, then we are making changes to our personality. We are essentially killing off false self images of our personality. These aspects and self images have a life of their own like any living being. They might very well respond with resistance and objection as any living being would to death.
Those habits that we seek to let go of fight to stay alive in our personality. When they react with fear to their impending end, we often mistake that fear as our own fear. We might feel as if we are somehow going to die and that is uncomfortable. In this way we resist change, even if the change will lead us to greater love and happiness.
Spiritual and religious traditions have often created ceremony and rituals around the death of false self images to help people move through this process. The bottom line is that if we wish to make changes in our behavior and happiness, we will need to let go of aspects of our personality and be willing to let them die. That process brings up a fear that we may be uncomfortable with. In order to make real change towards happiness and love in our lives we will need the skills to deal with this fear of change. This begins with awareness of what we are dealing with.