I started doing something a little while ago with my writing which has, I think, helped me. Simply put, I relate to my own work. If I’m writing an emotionally charged scene, I bring to mind something in my life which brought about a diluted version of the same emotion.
For example, if your character’s whole family has just perished, you might immerse yourself in the feelings you had when your pet hamster died. These are at opposite ends of a sliding scale of emotional intensity, but they are on the same sliding scale.
The same thing works for little details. You can chuck tiny shards of your life into a story, and it adds a genuine air. The downside to this, I find, is I do feel less inclined to share said story. People can tend to over associate author with content.
And finally, whatever you write, write it with confidence. There is a saying among writers; “Write what you know.” Taken literally, I would argue this is in fundamental disagreement with the pursuit of fiction writing. Lionel Shriver gave an excellent speech on fiction, writing what you know, and cultural appropriation, a written version of which you can find here.