I would like to know why you say that negativity is untrue.
Reality is true. Reality is a pure act of attention to what is at hand. There is no negativity in a pure act of attention to what is at hand. There is no negativity even in planning some action wherein you are weighing the risks versus reward factors. Even though the action (where you will be acting) may be in the future, the planning itself is a pure act of attention to what is at hand--planning. Actively planning something is as much being in the NOW as the future planned action per se would be being in the NOW (where you would be acting.)
Negativity would be involved in idle musing, not on-purpose thinking but passive thinking where you end up having downer thoughts and therefore downer feelings about people, places or things that you are not actively engaged with at the moment. These would be rambling thoughts about something in the past or something in the future. Feeling bad about the past or future is not giving a pure act of attention to what is at hand. It is not being situated in present reality and therefore, it is not "real" or "true" but "untrue."