I think we can get all twisted up when we over-analyse what we believe we should be thinking or feeling, vs what we actually do. The mind tends to manufacture things when it feels it's missing information. This is why most optical illusions work. If you feel that you should be feeling a certain way, but aren't, your mind may try to conjure up an approximation of what you think you should be feeling and present it to you. This may explain why it feels similar, but not. As far as the not feeling of the emotion directly, there are people who are not able to feel certain emotions, and the reasons can vary. Your brain could be wired differently than most, or you could just be stressed out. You could be dealing with emotional trauma. Or it could just be you focusing too much on the self. Like making it a thing is a self fulfilling prophecy. You are worried you don't feel fear, so your brain fixates on it, and it can't process it normally. An analogy might be how if you try to think about walking (tell your brain to lift right leg, bend at knee, shift weight forward, put right foot down, now lift left, etc you will fail to walk properly, but if you just relaxed and didn't think about it, you would walk normally.