What Triggers Irrational Behavior In People?

 Usually, there are four things:

1.  Drugs/booze.

2.  Stress. 

3.  A new and unique situation has unfolded, which does not meet the 'norm' that you accept or react to in some scripted way.  

4. People around you seem to bring in some new insight or created 'world', and you don't really show your skeptical side to 'protect' rational thoughts.