Narrow the scope of your story so that you have time and space to provide the details that give truth to your fiction.
Constantly observe the world around you to collect details that you can access when writing.
Remember emotions from the past and the physical correlatives of those emotions. Allow yourself to face your emotions honestly.
Draw on six senses when you write to give credibility: sight, sound, touch, smell, taste, kinesthetic sense. Kinesthetic sense is the internal physical sense of your body; for example, your rumbling gut, a piercing pain in your head, a stiff knee, shortness of breath. Emotions are often attached to the kinesthetic sense.
Everyday exercise your brain by dreaming. The dreaming prepares you to write with specificity that feels truthful.