I have a specific memory back during my school days, when certain phrases would become trendy and current and everyone was using them, of realising that sometimes you must make a conscious effort to start using a phrase if you want it to become part of your own speech. Then you find that things have gone too far, it's become a nasty habit, and you are using that word or phrase all the time!
Something similar happened to me when I was working in schools back in 2016-2018. The word 'cool' was gradually being replaced by 'sick' and both pupils and teachers would talk of "smashing" things in the sense of doing them well. I must confess that with regards to both these phrases, I made a conscious effort NOT to start using them, but that's just a personal choice!!
This kind of thing continues to happen to me all the time here in France; where I notice a colloquial turn of phrase, realise what it means, and want to start using it. Normally I miss the opportunity for weeks to begin with, but once I'm off, there's no stopping me! Here are some recent examples:
"de même". This is handy when you want to say, "same to you". For example, when someone wishes you a good day, or tells you it was nice to see you, and you wish to return the sentiment. You can also say; "et vous aussi", but de même is just a bit more colloquial and much more French! I'm well on the case with this one!
"C'est moi". In a similar kind of conversational exchange, I couldn't figure this one out at first. I would thank someone for doing me a service or helping me, and they would reply; "C'est moi" - it's me?!! I was really confused. No one had told me about this expression. I wanted to say, "Well I know it's you, that's why I'm thanking you!" But what they were really saying was short for "C'est moi qui vous remercie" - "it's I who thank you", which is the equivalent to the situation when we say in English; "No, no, thank you", with the emphasis on the word "you". I'm still a virgin when it comes to this phrase. I don't seem to have had the opportunity. But maybe it's because I haven't been giving other people cause to thank me for anything recently!!
"Tant qu'on y est". This is my most recent example. I've known what it means for ages, but this week I realised that I've never actually used it myself. Literally, it means "whilst one is there", as we might say in English "whilst we're about it" or "whilst we're at it". A bit like, "by the way". Now when I want to say, "by the way" in French, my default is "à propos", or "au fait". But my challenge to myself is to get "tant qu'on y est" into conversation in the next few weeks! Especially useful when you've got a builder or an 'artisan' around to fix something at your house, and as she/he's leaving you remember umpteen other little things that they might just do before they go!