As a human, you have many selfs or avataars in you. A current-self is a state with regular workings of life without any new change in the state – desire or hatred. The moment you have a desire (say to buy those new sneakers or that new mobile phone) you create a new state called the desired-self. And the stronger the desire, the stronger the comparison between the current-self and the desired-self. Once the desired-self is created, the current-self feels inadequate or lower in confidence or self-esteem or happiness because the comparison causes a deficit in the current-self. So, essentially your desires will make you feel low, but make you move forward in the direction of the desire.
Just the way a desire causes a desired-self, a hatred towards something causes an undesired-self. The stronger the hatred, the stronger the comparison between the current self and the undesired-self, making the current-self feel adequate and removing any necessity for change.
Fear can appear in both states of comparison basis how the self evaluates the work required to achieve the desired self or the work required to stop from turning into the undesired-self. Since entropy is by default present in nature, you almost always fear of everything that you hate, (the undesired self). On the other hand, you fear your desired-self if your desires are morally wrong and you battle internally. If your desires are morally correct, then you will go after it openly whereas if your desires are not morally correct then you will either suppress it or go after them secretly, but it will leave an undesired-self in another aspect of your self (avataar).
So, the most productive self-development happens in the areas of your moral desires as you can work on them with full energy without any negative impact on other selfs or avataars of your life.