Use 'slip up' when an error happens unintentionally, especially in informal contexts.

Accidental Error

'Slip up' implies the mistake was not done on purpose; it's a lapse in concentration or memory.

Not Deliberate

A 'slip up' is usually a minor mistake, not a major failure or disaster.

Use 'slip up' to describe losing balance suddenly, often due to a slippery surface or tripping.

A 'slip up' in this context is unexpected and can lead to surprise or immediate reaction.

This use of 'slip up' refers to physical action, not a mental mistake or error.