Most people appear relatively sane. Their lives have a certain system and consistency to them. They can explain their actions, they have recognizable patterns of how they do things, and their course of action is fairly predictable.
The widespread notion of sanity is that it consists of just those qualities: being "normal", consistent, predictable, able to explain one's actions logically, doing what others expect and consider acceptable.
It is common to have fears of anything that lies outside those norms. Anything that is different, inconsistent, unpredictable, unexplainable, and extraordinary is often considered dangerous and unsane. Particularly anything that is moving rapidly in forceful but totally unpredictable ways can easily be considered insane.
Commonly people have built a small element of unpredictability into their lives. A few surprises and a little weirdness becomes a spice of life. Different people have different degrees to which they tolerate unpredictability. But almost always there will be a limit that cannot be crossed without fear of insanity.
Now, really all of this is a rather upside down view of things. Fixedness and limitation are passing for sanity. Uncontrolled motion passes for insanity.
The truth of the matter is that the true nature of things always is dynamic. And if you look deep enough human logic always falls apart.
Attempting to hold that still which is really moving is the mechanic of any human aberration. Creating rigid mental structures and pretending that they are the real world.
If enough people agree on a certain set of limiting ideas, then they might succeed in convincing themselves or others that that is the way things really are.
Narrowing one's view to a certain limited reality can be quite interesting and educational. The trouble comes in if one takes it too seriously and thinks that it is the only real world.
Immediately above and below any limited reality is the unlimited dynamic reality. That goes both for looking deeper into the common physical reality, and also for looking deeper into one's own subjective reality.
In terms of physics, all the apparently solid and consistent things we are looking at, really aren't when we look close enough. A "table" might appear to be one thing that stays the same for a long time. But a table consists of trillions of atoms in rapid, apparently random motion. The same atoms don't even stay there, new ones arrive and old ones leave all the time. If we look even close we just see sub-atomic forces that appear in even more random motion. At the sub-atomic level we can't even point out that anything actually is there, and we would be hard pressed to point out where one thing ends and another starts. A table is a complex, continually changing collection of events. Simply naming it "one table" is a gross, gross over-simplification, although it is very practical in a human context.
Looking inside the mind, below any surface veneer of proper, orderly, moral thinking, you very quickly find a bubbling, boiling ocean of weird, unpredictable, and meaningless stuff. Many people hold on very tight to not let any of it out, but if they lower their defenses for a moment it is there. It is from here that creativity comes.
Freudians regarded this boiling ocean as something bad, as a collection of evil, anti-social, suicidal, perverted urges that needed to be controlled and kept down. Mankind would indeed have very sorry prospects if that was the case. Luckily it isn't. The perverted view is the one that regards Man's inner spiritual and creative nature as something evil that should be suppressed.
What could fool you at first glance is that if you just open a safety valve a little bit, after it has been closed for a long time, what comes out isn't necessarily pretty. If you have kept your emotions building up inside for years and then suddenly you open up, then it might very well be an unbalanced outburst of extreme rage. If there is prohibition and you acquire a case of whiskey then you probably get drunk. If people temporarily leave a morally controlled area and enter a more loose area they tend to indulge in all the things they usually can't do. They might smoke dope and watch porno movies 24 hours a day, just because they suddenly can.
There is a certain process that would happen. At first, if a safety valve is opened one would indulge in all the stuff that has previously been repressed and denied. After a while when one realizes that one can freely do that then things balance out. And then one would more do what one really wants to do.
The myth that people need to be controlled and repressed so their evil urges don't come out, is a dangerous one. The exercise of that principle is exactly the trigger of a great many unfortunate things in the world. If you take a person and suppress and control her for years, stopping her from saying or doing what she wants and feels, and then suddenly you give her a gun. Well, then she might suddenly decide to give vent to all the stuff she never expressed and that might very well be in a violent way.
The only way of really establishing a sane society would be to recognize the basic goodness in people and to allow them to express themselves. Aberration and violence come out of repression and artificial boundaries.
If you suppress people thoroughly and then you give them just a little bit of freedom, that can indeed be dangerous. The only safe thing to do is to set people free completely.
We can do that gradually. By prompting people to go beyond their usual behavior patterns and do actions that aren't based in their existing norms. Doing what their impulses and intuition tells them rather than what their morals and logic tell them. We can work through the different uncomforts and restrictions that surface. We can do that in different areas of life. Eventually a person can become able to act freely without embarrassment and limitation.
Only when a person is able to do any type of action freely will she be able to freely choose to do what she would most like to do. Incidentally that is always something constructive and enjoyable.