knock at your door

knock at (one's) door

To present (itself) to one as a possibility in the near future, especially temporarily. Usually refers to opportunities or desirable options. It was hard leaving my parents and all my friends from high school, but when an opportunity to attend school in Europe knocked at my door, I knew I had to seize the chance. What would you do if the chance to make half a million dollars was suddenly knocking at your door?
See also: door, knock

knock at your door

or

come knocking at your door

If something such as a problem or opportunity knocks at your door or comes knocking at your door, it is likely to happen soon or is starting to happen. All of his life he had been hankering after his personal freedom, and now freedom was knocking at his door, begging him to come in. During these tough economic times, feeling the spirit of happiness can be difficult, especially when the recession has come knocking at your door.
See also: door, knock