1.
If something falls apart, it breaks into pieces because it is old or badly made.
The work was never finished and bit by bit the building fell apart.
PHRASAL VERB: V P
2.
If an organization or system falls apart, it becomes disorganized or unable to work effectively, or breaks up into its different parts.
Europe’s monetary system is falling apart...
I’ve tried everything to stop our marriage falling apart.
= break down
PHRASAL VERB: V P, V P
3.
If you say that someone is falling apart, you mean that they are becoming emotionally disturbed and are unable to think calmly or to deal with the difficult or unpleasant situation that they are in. (INFORMAL)
I was falling apart. I wasn’t getting any sleep.
= crack up
PHRASAL VERB: V P