You've probably been wearing your bra wrong your entire life because of one little known rule.

Before we begin: I KNOW what you’re thinking. These days, women can’t go 40 seconds without hearing about something we’ve been doing wrong forever which is going to irrevocably ruin our lives (see: shaving, washing our hair, asking for raises, peeling a potato, using paper towels, etc etc etc).

But I’m not here to shame you. I’m here to help you.

And that’s why I’m forced to tell you: you’ve probably been wearing your bra wrong for a long, long time.

The good news? Fixing it could CHANGE YOUR LIFE (or at least save you the cost of a few bras over a lifetime).

I discovered this handy little tidbit of information only days ago in the David Jones change room, where a concerned bra fitter actually raised her voice and shouted at me for my terrible mistake.

My sin? I’d done the bra up on the tightest hook when I tried it on.

Nope, that's wrong. Image via iStock.

Apparently, when trying on a bra, you should only ever do it up on the loosest hook. If things feel too insecure, it's time to try on a bra with a smaller band size (for example, moving from a 12 to a 10).

The theory behind this is actually pretty sound: as your bra gets older, the band stretches. If you start off using the loosest hook, you can gradually tighten your bra as the strength of the elastic fades - but, if you start off with the tightest hook, you have nowhere to go.

That means you'll be back in the change room buying a new bra sooner - and nobody wants that (particularly not my disgruntled bra fitter).

Oh, and while we're here? According to The Sun, wearing the same bra two days in a row can make the elastic wear out much faster. That doesn't mean you have to wash your bra after every wear (nobody has time for that), but they do recommend you have three to five "daily" bras to rotate between to give that hardworking elastic a break.