I've been reading people most of my life
I've even had a few instances of telepathic communication.
I used to sense a deep dark depression in this woman with whom I worked, although outwardly all was normal. I finally asked her about it and told her what I was sensing and that I was concerned. She told me that every year at the same time she got very depressed for about 2 weeks around the anniversary of her son's death. Sure enough, a few days later I could sense that the depression had lifted. For another year at least.
In order to sense things, read people, first you have to be interested more in people and things around you than in yourself. Narcissists need not apply.