To mess up is to spoil something, or to make it untidy. Mess up the arrangements.
The spoiling sense is informal and takes blame, which is why people say it about themselves. To mess up a room and to mess up a plan use the same words and different tones.
1phrasemess upTo spoil something, or to make it untidy.
“One wrong date will mess up the whole schedule.”
mess up is a phrase.
Practised in Phrasal Verbs