The Die Hard star swore that he would never walk down the aisle once more following his split from actress Demi Moore in 1998.
However, he told W magazine that model Heming changed his perspective on life.
"I lasted one date," said Willis. "I went from 'F**k love' to 'Love is truly the answer'.
"I spent the last 10 years single and, for the most part, unhappy. In a dark place. I never thought that being with someone else was the answer."
Willis, 54, also said that since marrying the 32-year-old earlier this year, the couple can't help but express their love for each other in public.
"We're sickening. We make out in public. I know there's some rule that you're not supposed to be doing – what is it? Public displays of affection?" he added.
Willis and Heming exchanged vows in March in a Caribbean ceremony, before officially tying the knot during a civil service in Los Angeles later that month.