It's all about Emotions!

The market oscillates between Fear & Greed.

A trader oscillates between two extremes:

Euphoria & Depression.

The more a trader goes towards the extremes, the more volatile his boom & bust will be.

This makes the Boom & Bust Cycle!

A usual Boom & Bust Cycle looks like this:

Trader goes on a Winning Streak.

Gets extremely euphoric, thinks he's God.

His overconfidence causes him to take random trades, which result in losses.

He gets angry, starts overtrading, loses all his earnings and gets depressed.

He then promises to be disciplined.

Starts making some wins, gets euphoric again and repeats the cycle.