If you have a concentration spell and cast an offensive con spell that failed due st, do you loose your initial spell?

@JeremyECrawford If you have a concentration spell and cast an offensive con spell that failed due st, do you loose your initial spell?

— Lexar (@Lexar131) June 6, 2017

If you're concentrating on a spell, your concentration on it ends the moment you start casting another concentration spell. #DnD https://t.co/Vtb9SszGq5

— Jeremy Crawford (@JeremyECrawford) June 6, 2017

What if you don’t concentrate on it? Like let it take effect on the round it’s cast and don’t bother holding onto it? Doesn't matter. The moment you start casting it, the other spell is done.

— Jeremy Crawford (@JeremyECrawford) June 6, 2017