couldn't help it

couldn't help it

Said in regards to something that one has done because it felt irresistible or was unavoidable. Well, as soon as he said not to push the button, I just had to push the button—I couldn't help it! A: "Did you burn the bread?" B: "Ugh, yes, but I couldn't help it—the baby woke up from her nap at an inopportune moment."
See also: help
Farlex Dictionary of Idioms.

(I) couldn't help it.

There was no way I could prevent it.; I was unable to prevent something from happening.; I was unable to control myself. Sally: You let the paint dry with brush marks in it. Mary: I couldn't help it. The telephone rang. Fred: You got fingerprints all over the window. Mary: Sorry. Couldn't help it.
See also: help
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • as regards
  • as regards somebody/something
  • have a weakness for
  • have a weakness for (someone or something)
  • weakness
  • button down
  • a hard pill to swallow
  • a tough pill to swallow
  • talking of (someone or something)
  • talking of somebody/something
References in classic literature
I couldn't help it. So now we was both on our knees with our chins on a fence rail and gazing--yes, and gasping too.
Tom Sawyer Detective
I couldn't help it, Dinah; it was the baby's crying made me go--and yet I was frightened to death.
Adam Bede
I felt as if I couldn't help it. I had to go with him."
But when he came to the shop and asked me I felt I couldn't help it."
Of Human Bondage
"And nobody would even bother to write anything about us, not until the last couple of years when they couldn't help it because we've grown so much.
Leadership's changing face: how African-American, Asian-American and Latin American leaders communicate in a multicultural age