Louse up
Definition 1 of 1
Pro Tip 1/3Casual Usage
Use 'louse up' in informal settings, like conversations with friends, not in formal writing. 
I hope I don't louse up my speech in front of everyone.
Pro Tip 2/3Negative Outcome
'Louse up' implies a mistake leading to a negative result, showing disappointment or frustration. 
He really loused up our chances of winning the game.
Pro Tip 3/3Colloquial Origins
Originates from 'louse' being a pest; 'louse up' metaphorically means making a situation 'pest-like' or troublesome. 
Don't louse up your room by leaving dirty clothes everywhere.