Some spells require Focus which makes the caster unable to take any action other than movement, and must remain conscious to keep the effect of the spell active. Spells that require focus can be broken in the following ways:
At will.
When the caster takes any other action including defending or interacting with an object or environment..
When the caster takes damage and fails a contested Mystic roll to maintain the spell.
If the caster gains the Unconscious condition.