if things change from one moment to the next, they change quickly or frequently.

The plans are being changed from one moment to the next.

You never know from one moment to the next what kind of mood he'll be in.

• There but for the grace of God go I.
• Thereby hangs a tale.
• the received wisdom
• the red-carpet treatment
• the red-light district
• Therein hangs a tale.
• There is more to someone than meets the eye.
• There is more to something than meets the eye.
• there is never a dull moment
• there is no such thing
• there isn't a [mean, jealous, unkind etc.] bone in body
• there isn't a [mean, jealous, unkind etc.] bone in someone's body
• there is safety in numbers
• there'll be hell to pay
• there's a lot to be said for
• there's a lot to be said for doing something
• there's a lot to be said for something
• There's a time and a place.
• There's life in the old dog yet.
• There's many a slip twixt cup and lip.
• There's many a true word spoken in jest.
• there's method in madness
• there's method in someone's madness
• There's more than one way to skin a cat.
• there's much to be said for