当幸福来敲门，英文可以说成"when happiness comes knocking"。这个说法起源于一个英国人费茨·洛克（Fitz-Greene Halleck）的诗"Marco Bozzaris"，其中有句话是"Happiness is like a butterfly, which when pursued is just beyond our grasp, but, if you will sit down quietly, may alight upon you."，意思是幸福就像一只蝴蝶，当你追逐它时，它总是擦肩而过，但如果你安静地坐下来，它也许会停在你身上。换句话说，幸福是来自内心平静和安宁的。

一些例句：

When happiness comes knocking, don't ignore it. 既然幸福来敲门了，就不要无视它。

When happiness comes knocking, open the door and invite it in. 幸福来敲门时，打开门邀请它进来。

When happiness comes knocking, remember to be grateful. 当幸福来敲门时，记得要感恩。