How can I know the truth about anything? What I mean to say, is that if I am only me, and I only know my own experience in anything, then how can I know if it's normal or not?
You may well not be able to know. The color-blind sometimes go through much of their life not aware of the fact, and that is an issue which is easily testable.
Example: Many of us know people who are “not quite right,” but how many of those people are aware of it?
If you suspect others’ feelings or reactions are different from your own, perhaps you can ask them to describe them – if it sounds very different from your own experience, there may be a problem.
Eftach, my friend, if your experience does not include what you understand from others’ descriptions to be happiness, you may want to read up on depression – perhaps Dr. Twerski’s “Getting Up When You’re Down,” which I am fairly confident could not inspire you to misdiagnose yourself.
This question doesn’t bother you enough to interfere with living your life, does it?