society's norm
Society created what a normal reality is by creating jobs so our communities that we have built can function, farmers, butchers, grocery stores, jewlery makers, seamstress, etc. If you can function enough to drive a car, hold down a job, and be a safe parent, teching your children the general right and wrongs (for ex. it's wrong to hit people, it's right to take turns going down the slide). As long as you can function in a every day lifestyle in the home and at a job, then anything outside of that doesn't (for the most part) matter. People may find you extremely odd talking about seeing faeries, reading cards, and talking about poltergiets, but it doesn't classify you so strange that you would be considered "insane" by the science of psychology (one of my favorite areas of study).
Psychologists have a certain set guide line, that pretty much falls into what i explained above. When something falls out of line, say for instance, you feel melancholy, and for no reason, but you can still "function" in your daily routines, your still considered "normal", but maybe you have some underlying issues that are surfacing that need to be brought into the concious so you can better deal with the underlying problem. No one likes to be upset in any way. We don't like to be sad, mad, angry, etc. We do (most of us) like to be happy, in love, laughing, and sharing good times with the people in our lives that we relate to. However, there's a difference between, loosing your job and being upset about it, vs. just waking up one day and your upset to the point where you feel like you can't handle going into work, so you call in. When you stop being able to function, or continue on in even what you consider normal for yourself, in your own routine, is when you may have a problem. To call it insanity, well, i think the term insanity is used way too loosely, but you have to be pretty extreme to be considered insane. Most people do have problems with their libido, or with depression, or maniac depressive, or don't know how to communicate with their spouse, but on much smaller scales, and usually manipulated by events that happen in our lives. I can continue on forever so i'm going to stop here and anyone else that would like to jump in on this, feel free.