"the only Truth lies within oneself" as the hermetic wisdom goes. In any moment we have the choice to create our own sense of Love and Truth, and if we do so we'll be given evidence thereof. Yet we can also latch onto others' sense of Love and Truth and create accordingly, yet in doing so we'll eventually play victim to our circumstances and experience."I didn't want that in the first place" is then our directive, placing us into the position of blaming others, pushing away our responsibility for our life experience.
A Belief is pure energy form, as all thoughts are quantum energy, the least dense energy state. So in order for a belief to be manifested into denser forms it needs to be cultivated so that it gains power which will sooner or later pierce through into our five senses' vicinity.
This applies to any and all beliefs regardless of whether the thought is negative or positive. What we lay our focus on will create more of it, so beware of your thoughts. :)