Without much detail of what they were because they actually all are still hard limits for me but the three situations were:

One was just this past February right before the shutdowns... I was in session with one of my Dommes who I have an extreme affinity for (which is not actually the case with everyone I serve or even who have that special status of being considered to be one of my Dommes)... I don't allow post-session marks and she started hitting me with a dragon's tail so strongly that I couldn't believe it wouldn't leave a mark... Mentally I was struggling but I also have complete trust in her... Finally she got me with a final strike that may my mind explode in pain and I knew marked me... I didn't say anything but I literally spent the rest of the session trying to release my anger while she did wonderful things that should have put me in complete bliss. With literally anyone else I would have called red and discussed it, but I could tell that she was in the most intense Domspace and I literally couldn't be so selfish as to break that for her... especially knowing that wouldn't effect whether I had marks at that point or not (nothing we did after that came close to leaving a mark). I didn't even mention it at Dinner after because she was still in complete bliss and that is what I truly wanted. However, after it was all over I emailed her and told her what had happened and what was going on in my mind... She replied in utter agony because we had been together so much that she never even thought to review or ask about my lists again and didn't realize that was actually a limit for me.

Another had to do with poor communication because this particular Domme (who also enjoys that my Domme status) isn't a native English speaker and she sometimes misunderstands. There was something that she wanted to do that was past my limits but there is also stuff that I have wanted to do that is past her limits so I jokingly said I would be willing to gamble my limit against hers. She misunderstood this and brought another person into the session but essentially pulled activities out of a hat for the three of us. This particular person being in the session was actually the hard limit but I could not embarrass my Domme in front of that person by objecting after she had already arranged all of this. In the end, it was amazing to have to submit in this way but it is still not something that I would repeat or allow someone else to do.

For the first time I ever was pushed past a hard limit, it was extremely intentional by this Domme and is really what pushed her into that my Domme status (which only these three Dommes currently enjoy... Although there are three others who have at some point in the past). This was probably only a few years into sessioning with her (I have now been with her for more than a dozen years and it is very personal rather than professional at this point) and she worked to get me to do it over four or five sessions... Including even trying to physically force it and failing... But, finally she got me in the right headspace near the beginning of one session and very simply demanded/ordered/instructed me to do it and I just complied. It was complete and utter submission to her will and the most fantastic bliss imaginable. To this day, she randomly instructs or forces me to do it again in many ways and I actively crave it with her... but now it is one of my hardest limits for anyone else because it is just intensely special and to do it for anyone else would feel like I was cheating on her (she knows this and knows that she can order me to do so for someone else if she wants, but my never doing it for anyone else is special to her). At this point... I honestly don't think there is anything that she can't make me do but she is happy with that knowledge rather than needing to prove it over and over.

Hope that explains it in a way that makes sense.