be your own worst enemy
US /bi jʊər oʊn wɜrst ˈɛn.ə.mi/
UK /bi jʊər oʊn wɜrst ˈɛn.ə.mi/
1.
to cause most of your own problems because of your attitude or behavior
:
•
He tends to be his own worst enemy, always sabotaging his chances of success.
•
If you keep procrastinating, you'll be your own worst enemy when the deadline comes.