When I was at school I had the biggest crush on my best friend. I was so madly in love with him that I let him act in a not-very-best-friendly manner and never once complained. And by that I don't mean I let him sex me up and then treat me like shit in public, because when I was at school I looked like this:

No, he just used to take the piss out of me relentlessly, generally treat me a bit like a doormat....he must have liked me a bit because he laughed at all my brilliant jokes, but the way to a man's heart has never been via his sense of humour. It's via his sense of loving big tits and pretty faces. Neither of which I had back then. Or now actually.....oh fucking hell. Anyways, when we were 15 he got a girlfriend, a lovely mouthy chav with an IQ of 74 and a big pair of boobs. They went out for 5 years whereupon she cheated on him and he realised she was as about as much fun as a bag of cold sick.
When we were 15 I ended up having to endure an afternoon at his house with her there. I had a bra on that had removeable straps so you could wear it a number of different ways. Unfortunately whilst at his house one of the straps detached itself and sort of hung out of my top. No big deal, it wasn't like my boobs both fell out and nipples were everywhere, it was just the end of a bra strap poking out of my neckline. She saw it and went "oh my god! What is THAT!?". Instantly I was embarrassed. I went puce and was more mortified than I've ever been in my life. I shakily fidgeted with the strap until it was re-attached and she acted as though I'd been caught masturbating on the couch for the next hour until I finally left. The incident has left me with a sense of mortification for years (8 years!). Until yesterday. I was at work and my bra, a multiway bra similar to the one I was wearing in 2000, decided to release itself from one of the straps. The strap pinged out of my top and hung over the front. My colleague saw this happen and went "is that your bra strap?". I hurriedly re-attached it and nodded, devastated. She went back to typing and said "it's so annoying when that happens isn't it". Instantly I realised that I was a very different person to when I was 15 and that I'd grown up plenty.
And that is the story of how I learnt that it's OK to display a pinged-off bra strap once in a while.