I'm sure there are a lot of people who have trouble understanding their own emotions, or they simply don't ever try.

I've been trying for a long time, and I've come up empty handed. I think that, on a fundamental level, I understand and process emotions differently than other people. Consequently, when normal people try to explain these things to me, it just sounds like woo and fairy magic.

As for psychopaths and narcissists and their feelings. Like Open Eyes said, narcissists are capable of experiencing all emotions. They're even hypersensitive when it comes to anything that might bruise their ego. They just don't empathize. And they probably have the capacity to empathize if pushed hard enough, but they waste too much energy preserving their own fragile sense of self.

Primary psychopaths do not experience the full spectrum of human emotion. They do experience the basic lizard emotions, like startle response or adrenaline rushes, and the prospect of "winning" to a psychopath can elicit feelings not unlike those felt after doing a line of cocaine. They're also sensitive to frustration, especially while they're in the aforementioned state and the source of frustration is impeding them from whatever goal they're after. They'll react to frustration with intense fits of rage that disappear as quickly as they came. Also, what few emotions they do have are very fleeting. If I recall a memory of an emotional event in my life, there isn't any emotion associated with the memory, even if I know that I was emotional at the time it took place.