The one I remember most came about four to five years ago, in chemistry class. Before Easter holiday, we had been learning about a purification process called recrystallization. When we got back from the holiday my teacher asked if anyone knew what the topic we studied before was called. I did, but didn't want to speak up, the class was silent. My chemistry teacher was a lovely lady, but when she was annoyed she got really annoyed. So she started getting increasingly annoyed, asking if really no one remembers what we did not even three weeks ago. I can see everyone is looking around awkwardlt for a saviour, because we all know the arse-chewing that's coming. I decide I have to go for it. As soon as I opened my mouth and began the "r-" my teacher knew I had it, and her expression immediately changed to pleased reassurance. But not only was the r- at the start of the word extremely difficult. But moving on to the -cr- sound immediately after was just impossible. I went through two lung-fulls of air struggling with that word. Throughout I could see the rest of the class shifting awkwardly. And my chemistry teaching looking at me, smiling, and nodding her head. Eventually after the third breath I managed to wheeze out a breathless "recrystallization", which I'm pretty sure no one heard but thankfully the teacher took it and carried on with the lesson. I felt so frustrated in the moment, not just at myself but at the class for putting me through it. Afterwards I just felt so embarrassed and exhausted. I think this is definitely part of why I like people to finish my words for me. I hate the feeling of everyone waiting on you, whilst you try and fail to say something everyone already knows.