They point to this man or to that, and how he seized a chance--or how, perhaps, he failed to do so.
"If ever an opportunity like that comes tae me," ye'll hear them say, "just watch me tak' it! Opportunity'll ne'er ha' to knock twice upon my door." All well and good.

But opportunity is no always oot seekin doors to knock upon.

Whiles she'll be sittin' hame, snug as a bug in a rug, waitin' fer callers, her ear cocked for the sound o' the knock on _her_ door.

Whiles the knock comes she'll lep' up and open, and that man's fortune is made frae that day forth.

Ye maun e'en go seekin' opportunity yersel, if so be she's slow in coming to ye.