Lose It Meaning

(idiomatic) To lose control of a situation.

Example:   When my dad found out I had failed the exams, he just lost it.
To begin to laugh uncontrollably.
  When the teacher's chair broke, the class completely lost it.
To lose one's mind, go crazy.
To cease to have a skill or ability, to lose one's touch, to be washed up.
  When you think about all she's done for the sport, it's kind of sad, but she's completely lost it over the past few years.